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Nobel Prize in Physics 1921

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Why we should thank Einstein for our smartphone cameras

Learn more about how the photoelectric effect has shaped technologies such as burglar alarms, solar panels and the camera in your smartphone.

Read the story

Credit: Getty Images

From the glow of blue LEDs to the ‘miracle’ of IVF. These six discoveries not only improve our daily lives, but save them and help create new ones.
Read more

A chance discovery made around 80 years ago paved the way for Mary Brunkow’s painstaking work, which contributed to redefining how the immune system functions. Read more about the 2025 medicine laureate and how she has embraced the unexpected throughout her career.

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Mary Brunkow showing the slides for her thesis defense, 1990. Credit: Mary Brunkow

[H2]

Enter your birthday to find out.

[IMG: Kailash Satyarthi and the 2014 Nobel Laureates during his visit to the Nobel Foundation]
Kailash Satyarthi and the 2014 Nobel Prize laureates. © Nobel Prize Outreach. Photo: Alexander Mahmoud

Watch the conversation with Nobel Prize laureates Stefan Hell and Benjamin List, investigating the evolution and progress of science.

[IMG: Stefan Hell 08]
Photo: © Fundación Ramón Areces

[H1]
The man behindthe prize

In his last will, Alfred Nobel specified that the bulk of his fortune should be used for prizes to “those who, during the preceding year, shall have conferred the greatest benefit to humankind.”

Learn more about Alfred Nobel

Stockholm, Nobel Prize Museum

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See images, books and instruments representing many centuries of exploring the smallest details in our body.

Oslo, Nobel Peace Center

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An exhibition about peace through the ages.

Oslo, Nobel Peace Center

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The fight for democracy in Venezuela has become a symbol of a broader global challenge.

This year’s Nobel Prize announcements will take place on 5–12 October. All of the prize announcements will be broadcast live on the official digital channels of the Nobel Prize. In-depth information about the prizes will be published here at nobelprize.org.

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The door to the Swedish Academy. Photo: K. Svanholm.

The first design of the Nobel Center project is here – a public building in Stockholm, Sweden for science, literature and peace. It will be an international symbol of knowledge, focusing on the Nobel Prize laureates’ stories and groundbreaking achievements. Read more about the project.

[IMG: View from the water along the quay.]
View from the water along the quay. The Nobel Center consists of four interconnected volumes that relate to the buildings of Södermalm and the size and height of the buildings in Gamla stan, on the other side of the water. The choice to use a wooden frame and reclaimed bricks reduces the impact on the environment. Bricks have characterised the architecture of Stockholm for centuries. The red shade is found in Stockholm’s classic brick buildings, such as City Hall. © Onirism/Nobel Prize Outreach

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Exploring life’s smallest details

Learn more about some of the Nobel Prize-awarded discoveries in the fields of cells, nerves and genes.

Nobel Minds

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Laureates discussing research, discoveries and achievements

Since the 1960s, Nobel Prize laureates have gathered for a roundtable discussion for television.

Watch Nobel Minds 2025

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Explore powerful moments and life-changing discoveries.

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Join thousands of global subscribers enjoying the free monthly Nobel Prize highlights, trivia and up-to-date information.

[IMG: Blood typing game]

How much do you know about blood types? Try out in this game.

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Learn about conditioned reflexes in this interactive game.

[IMG: Vitamin B1 educational game]

This fast-paced game relies on a keen knowledge of food containing vitamin B1.

Edmund Phelps died on 15 May 2026, aged 92. He was awarded the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel 2006 “for his analysis of intertemporal tradeoffs in macroeconomic policy.”
Biography

[IMG: Edmund S. Phelps]

J. Michael Bishop passed away on 20 March 2026, aged 90. He was awarded the Nobel Prize in Physiology or Medicine 1989 “for their discovery of the cellular origin of retroviral oncogenes.”
Biography

[IMG: J. Michael Bishop]

Christopher A. Sims died on 14 March 2026 in Minneapolis, Minnesota, USA, aged 83. He was awarded the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel 2011 “for their empirical research on cause and effect in the macroeconomy.”
Biography

[IMG: Christopher A. Sims]

Anthony Leggett passed away on 8 March 2026, aged 87. He was awarded the Nobel Prize in Physics 2003 “for pioneering contributions to the theory of superconductors and superfluids.”
Biography

[IMG: Anthony J. Leggett]

A painting by Swedish artist Emil Österman depicting the founder of the Nobel Prize, Alfred Nobel.

© Nobel Prize Outreach. Photo: Alexander Mahmoud

[H1]
The man behind the prize – Alfred Nobel

Alfred Nobel was an inventor, entrepreneur, scientist and businessman who also wrote poetry and drama. His varied interests are reflected in the prize he established and which he lay the foundation for in 1895 when he wrote his last will, leaving much of his wealth to the establishment of the prize.
Since 1901, the Nobel Prize has been honouring men and women from around the world for outstanding achievements in physics, chemistry, physiology or medicine, literature and for work in peace.

Alfred Nobel signed his last will in Paris on 27 November 1895. He specified that the bulk of his fortune should be divided into five parts and to be used for prizes in physics, chemistry, physiology or medicine, literature and peace to “those who, during the preceding year, shall have conferred the greatest benefit to humankind.”

[IMG: Alfred Nobel will (2)]
The will of Alfred Nobel. © Nobel Media. Photo: Alexander Mahmoud

1833
Alfred Nobel is born in Stockholm, Sweden. In the same year, his father, Immanuel Nobel, goes bankrupt.

1838
Immanuel Nobel arrives in St Petersburg, Russia, where he starts a mechanical workshop; he leaves his family behind in Sweden. He lands a contract with a Russian general, who is interested in the Swedish inventor’s designs for sea and land mines. His business flourishes and evolves to a large mechanical engineering company.

1842
The Nobel family is reunited in St Petersburg, Russia.

1850 – 1852
At the age of 17, Alfred Nobel speaks five languages fluently. He travels to Paris and works for one year in the laboratory of T. Jules Pelouze. He also travels to Italy, Germany and the United States (US).

1853 – 1856
Immanuel Nobel’s company goes bankrupt as the Crimean War ends and the Russian military cancel orders. Alfred Nobel searches desperately for new products. Nikolai N. Zinin, Nobel’s chemistry teacher, reminds him of nitroglycerin.

1862
Alfred Nobel starts his experiments with nitroglycerin.

1863
Alfred Nobel moves back to Stockholm and obtains the first patent on nitroglycerin (blasting oil) as an industrial explosive.

1864
Alfred Nobel patents a detonator (blasting cap) for triggering the explosion of nitroglycerin and forms the company Nitroglycerin AB. Emil, Alfred Nobel’s brother, is killed during the preparation of nitroglycerin at Heleneborg, Stockholm.

1865
Alfred Nobel improves the blasting cap design and moves to Germany to set up the Alfred Nobel & Co Factory in Krümmel near Hamburg.

1866
A violent explosion destroys the Krümmel plant in Germany. Experimenting on a raft anchored on the river Elbe, Alfred Nobel tries to make nitroglycerin safer to handle. He finds that nitroglycerin is stabilised by the addition of kieselguhr (a siliceous deposit; also known as diatomaceous earth) and calls this mixture dynamite. (From Greek dynamis meaning “power”). He also establishes the United States Blasting Oil Company in the US.

1867
Alfred Nobel obtains a patent for dynamite in Sweden.

1871
Alfred Nobel establishes the British Dynamite Company (Ardeer, Scotland, UK). In 1877 the company name is changed to Nobel’s Explosives Company.

1872
Immanuel, Alfred Nobel’s father, passes away.

1873
At the age of 40 Alfred Nobel is a wealthy man. He moves to Paris and settles at Avenue Malakoff. The manufacture of nitroglycerin and dynamite starts at Ardeer, Scotland, UK.

1875
Alfred Nobel invents blasting gelatine in Paris and establishes Société Générale pour la Fabrication de la Dynamite in Paris.

1876
Alfred Nobel obtains a patent on blasting gelatine. Dynamitaktiengesellschaft (DAG), formerly Alfred Nobel & Co (Hamburg, Germany), is formed. Alfred Nobel advertises for a housekeeper/personal secretary, meets with Bertha Kinsky von Chinic und Tettau (later von Suttner) and hires her. She leaves her employment after a short time and becomes a leading peace activist.

1880
Dynamite Nobel is formed by merging Nobel’s Italian and Swiss companies.

1881
Alfred Nobel buys an estate and laboratory at Sevran outside Paris.

1885
German Union is formed by merging Dynamitaktiengesellschaft (DAG) and a group of German dynamite companies.

1886
Nobel-Dynamite Trust Co (London, UK) is formed by merging Dynamitaktiengesellschaft (DAG) and the Nobel’s Explosives Company.

1887
Nobel obtains a patent for the blasting powder “ballistite” in France.

1889
Andriette, Alfred Nobel’s mother, passes away.

1891
Alfred Nobel leaves Paris and settles in Sanremo, Italy, after a dispute with the French government over ballistite.

1893
Alfred Nobel hires the young engineer Ragnar Sohlman, who he later names executor of his will and testament.

1894
Alfred Nobel buys a small machine works (Bofors-Gullspång) and a manor (Björkborn) at Karlskoga, Sweden.

1895
The third and final will of Alfred Nobel is signed at the Swedish-Norwegian Club in Paris.

1896
Alfred Nobel dies, at the age of 63, in his home in Sanremo, Italy, on 10 December 1896.

1901
The first Nobel Prizes are awarded on 10 December.

Alfred Nobel was born in Stockholm in 1833. His father, Immanuel, was an inventor and it was in his father’s footsteps that Alfred would follow.

[IMG: Alfred Nobel 1853]

The young Alfred grew up, received his education and was shaped as a human being in the cosmopolitan atmosphere of St. Petersburg.

At forty years old, Alfred Nobel bought an elegant mansion in Avenue Malakoff, a fashionable quarter near the Arc de Triomphe and Bois-de-Boulogne

Björkborn, a property in Karlskoga, became Nobel’s last home in Sweden.

Alfred Nobel died on 10 December 1896 in his villa overlooking the Mediterranean in Sanremo, Italy.

“Home is where I work and I work everywhere.”
Alfred Nobel

More aphorisms

Based on Alfred’s work and patents a whole new industry developed. Within ten years, 16 explosives producing factories had been founded in 14 countries.

[IMG: Nobels Dynamite 10 Nov 1906]
Alfred Nobel's dynamite, 1856. Photo: Public domain.

Alfred Nobel’s first company, Nitroglycerine Aktiebolaget, had its explosives plant on an isolated inlet of Lake Mälaren.

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Alfred Nobel established his first overseas company in Krümmel, Germany.

[IMG: The Krümmel factory in 1915.]

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Alfred Nobel turned his sights to Scotland when Great Britain proved to be a difficult place to establish an explosives factory.

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Looking for a suitable location for his experiments near his home, Alfred Nobel found Sevran, 16 kilometers northeast of Paris.

[IMG: German Patent]

Alfred invented dynamite and experimented in making synthetic rubber, leather and artificial silk among many other things.

Learn more about the Swedish inventor

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Who was Alfred Nobel?

On 21 October 1833 a baby boy was born in Stockholm, Sweden who was to become the founder of the Nobel Prize.

Discover more

Alfred Nobel went through philosophy from antiquity to modern times, pointing out what he perceived to be vital issues.

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Alfred Nobel's compass. © Nobel Prize Outreach. Photo: Nanaka Adachi

“Isn’t it the irony of fate that I have been prescribed N/G 1 (nitroglycerine) to be taken internally!”

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Alfred Nobel’s old bottles. © Nobel Prize Outreach. Photo: Dan Lepp

Alfred Nobel’s thoughts on war and peace were set out in many years of correspondence with Bertha von Suttner.

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Letter from Alfred Nobel to Bertha von Suttner, 1983. The National Archives, Stockholm

Alfred Nobel had a big interest in literature and writing. He left behind a private library at Björkborn with over 1,500 volumes.

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Photo: The Nobel Museum in Karlskoga, Sweden

Alfred Nobel’s collection of books bears testimony to both the depth and breadth of his reading.

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Loneliness, reflection on the meaning of Life and the origin of the universe provide the fundamental themes of Alfred Nobel’s poetry.

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Alfred Nobel's poem 'The Riddle'. © Nobel Foundation Archive

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Microscopes play a key role in advancing research, in part thanks to the work of Nobel Prize laureates whose breakthroughs have allowed the tool to evolve.

[IMG: Human stem cell embedded in a 3D matrix, Cryo SEM.]

Join the conversation between 2025 physics laureate John Martinis and PhD student Eleonora Svanberg on curiosity and the future of quantum technology. Martinis reflects on the choices that led him to exploring quantum mechanical behaviour and discusses his groundbreaking work – conducted with co-laureates Michel Devoret and John Clarke – demonstrating quantum phenomena on a macroscopic scale.

Nobel Prize-awarded work on microwaves revolutionised our ways of communicating and helped us understand the origins of the universe.

[IMG: Image of beams of light depicting the cosmos, combined with a wave symbol.]

Nobel Prize in Literature 1976
Listen to Saul Bellow talk about his memories from 1920’s Chicago, the city where he grew up and used as a backdrop for his stories.

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Nobel Prize in Physics 1976
The discovery of a new heavy particle, J/psi, opened a new field of research.

Nobel Prize in Chemistry 1976
This work improved our understanding of how atoms bind together within molecules.

Nobel Prize in Physiology or Medicine 1976
Their work defined completely new principles for the behaviour of infectious diseases.

Curious to know what was served at the 1976 Nobel Prize banquet dinner? Browse the banquet menu archive.

Nobel Peace Prize 1976
A deadly tragedy motivated Betty Williams and Mairead Corrigan to found a movement to put an end to the conflict in Northern Ireland.

[IMG: Betty Williams and Mairead Corrigan]

Prize in economic sciences 1976
An influential economist of the second half of the 20th century, Milton Friedman became one of the leaders of the Chicago school of economics.

[IMG: Milton Friedman]

[H1]
How X-rays and crystals revealed the true nature of things

Read the story behind the 100-year-old discovery that continues to render Nobel Prizes.

A help in solving crimes and a revealer of history’s secrets: radiocarbon dating is one of the keys that unlocks our world.

[IMG: Montage showing a frog on a bamboo stick, a separate frog skeleton, and a countdown clock]

[H1]
Five spellbinding works by Nobel Prize laureates

Much like fairy tales, magical realism novels blur the lines between fantasy and reality.

Learn more

Listen to 2025 literature laureate László Krasznahorkai talk about the book that made him become a writer.

Nobel Prize in Literature 2015
Svetlana Alexievich’s new book tells the stories of young people who took to the streets in Belarus in 2020, protesting the election that was widely regarded as rigged.

[IMG: Svetlana Alexievich]

Nobel Prize in Literature 2024
Han Kang on imagination, how writing has changed her and what books mean to her.

Nobel Prize in Literature 1993
Read and listen to Toni Morrison’s Nobel Prize lecture.

Nobel Prize in Literature 1996
Read Possibilities and more poetry by Wisława Szymborska.

Nobel Prize in Literature 1945
Gabriela Mistral crossed over from teaching to politics and became one of Chile’s most celebrated poets.

Nobel Prize in Physiology or Medicine 1930

[H1]
Finding the key to safe blood transfusions

Today, we take it for granted that people have different blood types. But not so long ago, it was believed that all blood was the same – a fatal misunderstanding.

Read more

Close up of A positive blood in bag.

Credit: ER Productions Limited/Getty Images

International Committee of the Red Cross (ICRC), Nobel Peace Prize 1917, 1944 and 1963
Makur Diet lost his leg to a bullet in war-damaged South Sudan.

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UNHCR, Nobel Peace Prize 1954 and 1981
Kamal Hussein is a beacon of hope for Rohingya families torn apart by violence and ethnic cleansing.

ICBL, Nobel Peace Prize 1997
For the all-female team of Yazidi deminers, one wrong move means certain death.

IPCC, Nobel Peace Prize 2007
Follow one team’s extraordinary mission to help understand how climate change is affecting our planet.

Nelson Mandela, Nobel Peace Prize 1993
This orchestra uses the power of music to help South Africa overcome decades of violence and division.

[H1]
High hopes for quantum technologies

Applications of quantum technologies are anticipated to improve our daily lives and contribute to solving global challenges.

Explore the contributions, careers and lives of women who have been awarded Nobel Prizes for their scientific achievements.

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Photo: Johns Hopkins Medicine

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The unseen enemy: navigating antimicrobial resistance

The hunt is on to find new antibiotics with the potential to save millions of lives.

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Follow Ishrat Rahim who vaccinates children against polio in Pakistan.

[IMG: An illustration of helicobacter pylori]

Over the years, Nobel Prize-awarded advances in medicine show that remarkable progress is possible.

[IMG: Nobel Prize laureate Tasuku Honjo, surrounded by his team at Kyoto University]

Read about how scientists found ways to use the immune system to treat cancer.

Despite the Nobel Prize-awarded discovery of insulin and advances in diabetes treatment, amputations continue to devastate communities around the world. Follow Dr Foluso Fakorede, who fights to save lives in the Mississippi Delta.

The discovery of insulin and subsequent breakthroughs by Nobel Prize laureates led to advancements in how we treat the chronic disease.

[IMG: Original black and white photograph showing Banting, assisted by Sadie Gairns, performing surgery on a dog. Unidentified man in background.]

Dorothy Crowfoot Hodgkin used X-ray crystallography to “see” the molecules of penicillin, vitamin B12 and insulin.

[IMG: Dorothy Crowfoot Hodgkin]

The 2024 chemistry laureate believes that progress in science is made by working together and sharing ideas. Listen to him talk about how he sees mentoring as one of the most essential parts of his job.

[IMG: David Baker]

Hear the 2024 physics laureate talk about the development of AI, his fascination with understanding the human brain and how his family legacy of successful scientists put pressure on Hinton to follow in their footsteps.

[IMG: Geoffrey Hinton]

“Asking is hard. Once you realise there’s an interesting question to develop answers to, it is even harder.” Listen to the 2024 economic sciences laureate.

[IMG: Daron Acemoglu]

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Family matters

Meet the families with Nobel Prizes.

Read the story

Aage Bohr and Niels Bohr on the occasion of the defence of Aage's doctoral thesis, 1954.

Photo: Niels Bohr Archive, Copenhagen.

Nobel Prize-awarded breakthroughs

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A century of life-changing discoveries

Electronic devices help us in our daily lives, while innovations in medicine make life more manageable for people with chronic conditions.

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An icon in the world of modern science

Marie Curie is the only individual to receive the Nobel Prize in two different science categories.

Read her story

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11 prizes that help us understand and value our Earth

From understanding climate change to using AI to better protect our planet.

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An unrelenting opposition to Earth’s most dangerous weapons

A number of Nobel Prize laureates have worked to highlight the catastrophic humanitarian consequences of nuclear weapons and to strengthen international efforts to ban testing.

Read more

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Credit: Getty Images

[H1]
Why we should thank Einstein for our smartphone cameras

Learn more about how the photoelectric effect has shaped technologies such as burglar alarms, solar panels and the camera in your smartphone.
The engineer picked up a camera flash gun, aimed it at the tiny circuit board computer on the desk, and fired. For a fraction of a second, light flooded the room. Everyone blinked – and saw that the computer had crashed.
[H2] The Raspberry Pi team had just confirmed that their product, a budget computer sold to schools and electronics enthusiasts, hated having its picture taken. At least when you took the picture with a big xenon flash lamp.
[IMG: Raspberry Pi 2]
The Raspberry Pi 2 (model B.) Evan-Amos, Public domain, via Wikimedia Commons
“We all had fun crashing it,” recalls Eben Upton, founder of Raspberry Pi. They had realised that a chip on the computer was susceptible to the photoelectric effect – when light triggers the release of electrons, and thus an electrical current. A kind of reverse “light switch”, if you like.
Upton and his colleagues had not anticipated this problem. It was discovered by a Raspberry Pi 2 user less than a week after the device went on sale in early 2015. In subsequent versions of the computer, the troublesome chip featured a black coating thick enough to soak up incoming light.
More than a century earlier, Albert Einstein had described the photoelectric effect in a ground-breaking paper – one of four seminal papers he published in 1905 while working as a clerk in the Swiss patent office. Later, in 1921, he received the Nobel Prize in Physics for it, which he collected in 1922.
The photoelectric effect has gone on to shape all kinds of technologies – from burglar alarms to solar panels and the camera in your smartphone.
[H2] ‘Weird phenomena’

[IMG: Albert Einstein lecturing in Vienna]
Albert Einstein lecturing in Vienna, 1921. Photo: Ferdinand Schmutzer. Public domain via Wikimedia Commons
To understand it better, consider the question that gripped Einstein back in 1905: what is light made of?
At the time, many scientists theorised that light existed purely as a wave, which some suggested travelled across the universe in an intangible “light-bearing ether”. But to Einstein, this idea seemed ridiculous – “like Father Christmas”, says Steve Gimbel at Gettysburg College in the US.
Scientists including Heinrich Hertz had already demonstrated versions of the photoelectric effect by using light to generate tiny sparks, or to electrically charge pieces of gold leaf, causing them to repel each other.
“There were certain weird, unexplained phenomena where light could create electricity and that just blew people’s minds – that seemed to make no sense,” says Gimbel.
[IMG: Illustration of electromagnetic spectrum]
In the electromagnetic spectrum, visible light sits between infrared and ultraviolet radiation. Credit: BBC
The weirdest thing was that the intensity of light didn’t affect the energy of the electrons produced whereas the frequency, or colour, of the light did. This was mind-boggling. More light should mean more energy, right?
Well, Einstein realised that if light wasn’t just made up of waves but also discrete packets or particles (which later came to be known as photons) travelling in waves, then it could be that the energy of those individual particles would explain this.
“When a single photon hits an electron, it [the electron] gets excited,” explains Paul Davies, at the University of York. So long as that photon lands with enough energy, then the photoelectric effect occurs – and the electron is freed from the material.
Think of it like throwing tiny sticks of dynamite into an open barrel of cannonballs. The little explosions won’t be enough to knock out a cannonball, no matter how many times you fling one in. But if you use stronger dynamite, with more energy, that will make the cannonballs fly.
The energy value of a photon is directly related to the colour of visible light – photons in blue light travel on shorter waves and have more energy than those in red light, for instance. That’s why Hertz found that especially energetic ultraviolet light would produce stronger sparks during one of his experiments.
[H2] Foghorns and photovoltaic cells

Gimbel stresses that Einstein didn’t come up with this theory out of nowhere. He drew not only on work by Hertz and others, but also on physicist Max Planck’s theory of “quanta” – the idea that radiation, including light, consists of discrete packets of energy, for which Planck also received a Nobel Prize in Physics, in 1918. But in 1905 this concept was still controversial.
[IMG: Nobel Laureates Walther Nernst, Albert Einstein, Max Planck, Robert A. Millikan and Max von Laue]
From left to right: Nobel Prize laureates Walther Nernst, Albert Einstein, Max Planck, Robert A. Millikan and Max von Laue at a dinner given by von Laue in Berlin, 11 November 1931. Nationaal Archief, Photographer unknown, Public domain via Wikimedia Commons
“Einstein had this revolutionary mind where he was willing to consider other approaches,” says Gimbel. “He took seriously this idea that light could be quantised.”
[H2] Einstein’s work was divisive – especially his special theory of relativity. Some members of the Nobel physics committee at the time hesitated to award him a prize and, when they did, they chose to award it for his work on the photoelectric effect, rather than relativity.

Scientists have long debated whether this was the best choice but there is little doubt that harnessing the photoelectric effect has changed the way our world works, since so many technologies rely on it.
Motion sensors in burglar alarm systems, for example, emit a beam of infrared light. When this beam is interrupted by an intruder, the light received by the sensor changes, altering the electrical current – and that sets off the alarm.
[IMG: Illustration of camera, solar panels and x-rays]
Technologies like photo and image sensors rely on the photoelectric effect. Credit: Getty Images
Finish lines at races held in the Olympic Games have used photoelectric cells to detect exactly when runners cross. Such technology has allowed ships to sense fog, and automatically switch on foghorns. It has also enabled cars to turn on their windscreen wipers spontaneously when it rains.
Strictly speaking, the photoelectric effect refers to a phenomenon in which electrons escape a material – but Davies says this is closely related to the photovoltaic effect, where movement of electrons facilitates an electrical current flowing through adjacent materials.
That’s what solar cells in solar panels do when they turn sunlight into electricity, contributing clean, renewable energy to electricity grids and tackling climate change.
[H2] Silicon sensors

Another popular application of the photoelectric effect is in camera sensors, the light-sensitive part of a digital camera that captures images. Nearly all use CMOS technology, which was fine-tuned at Nasa in the 1990s for use in space, but came to be installed on billions of smartphones. “The CMOS image sensor was the perfect device, let’s say, for that. It turned out to be the killer application,” says engineer Eric Fossum, who worked on the project.
Silicon is the key material used in CMOS sensors and Fossum, now at Dartmouth College, notes that the photoelectric effect in silicon is triggered by many colours of light.
“It doesn’t matter whether it’s green light, red light, or blue light – a photon will liberate exactly one electron. We’re kind of lucky that way.” This really helps when you want to capture a subject’s colour in full detail.
[IMG: CMOS sensor]
Most smartphone cameras use CMOS sensors. Credit: Getty Images/BBC
Now, Fossum and colleagues are working on image sensors sensitive to the smallest imaginable amount of light – a single photon. These devices, also known as photon-counters, are already used for laboratory experiments but they could also revolutionise digital imaging technologies, for example by improving image quality in medical CT scanners, and exposing patients to less radiation. The potential applications don’t stop there. “We’ll have the capability to practically see in the dark with this new technology,” says Fossum.
Another scientist working on devices that harness the photoelectric effect is Dimitra Georgiadou at the University of Southampton. She and her colleagues are developing technologies that can detect light and process information about it without having to send data to a central computer system for analysis. “This reduces significantly the amount of energy it needs,” says Georgiadou.
This might help researchers develop highly advanced bionic eyes and give sight to blind people by enabling the design of smaller, easier to implant, and more energy-efficient devices. It could also enable self-driving cars to make faster decisions about when to brake for safety reasons.
[H2] Lunar glow

The light-sensing technology Georgiadou is focused on does not rely on silicon but rather organic, carbon-containing, materials – these can be tuned to respond only to specific colours of light, and also printed on flexible substrates.
Such technology could turn up in wearable, low-power light sensors able to track the heart rate and blood oxygen levels of premature babies, for example, by shining small amounts of light through their skin and into their veins.
Since Einstein wrote down his theory on the photoelectric effect in 1905, we’ve certainly come up with a lot of fun things to do with it. But there’s more. Understanding this incredible interaction of light and matter has revealed curious details about the way the universe works.
In the 1960s, some of the earliest moon landers took pictures of the lunar horizon and noticed something strange: a weird glow, almost like a gently fading sunset. Except that the moon doesn’t have an atmosphere like Earth’s, and it’s the scattering of light by particles in our atmosphere that creates sunrises and sunsets as the planet turns on its axis.
Where was this lunar glow coming from? It turned out that light from the sun was striking dust on the moon’s surface and, through the photoelectric effect, giving it a positive electrical charge.
These little dust particles thus repelled each other, periodically levitating above the lunar surface. As they did so, they caught the light of the recently set sun – and created that magical glow.
By Chris Baraniuk, BBC World Service. This content was created as a co-production between Nobel Prize Outreach and the BBC.
Published May 2026

[IMG: Albert Einstein]

[H3]
Albert Einstein

Nobel Prize in Physics 1921
for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect.

[IMG: Max Karl Ernst Ludwig Planck]

[H3]
Max Karl Ernst Ludwig Planck

Nobel Prize in Physics 1918
in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta.