MYTUTOR SUBJECT ANSWERS

951 views

What does the double slit experiment tell us about light?

Imagine an opaque barrier (no light can get through) with two parallel slits in it, onto which we shine a coherent light source (light of only one wavelength and in phase - a laser, for example, can produce this). There is a screen behind the barrier and slits.

 

What will the pattern on the screen look like?

 

If light was made up of tiny particles, like spraying tiny pellets towards the slits, we would expect that the particles which went towards a slit would fly straight through and land on the screen, forming two bright lines on the screen - one behind each slit. The photoelectric effect tells us that light acts with a particle nature, so this is what we should expect.

 

However this is not what we see with light!

 

With light, the pattern that emerges on the screen is a series of bright and dark bands, alternating across the screen (not just two bright bands). This is known as an interference pattern. This pattern is exactly what we would see if we had passed a water wave through the slits - strips where the wave was high and strips where the water was still. This results from the interference of waves.

This demonstrates that light has a wavelike nature, which seems to be contrary to what the photoelectric effect demonstrated. 

 

So which one is wrong?

 

Neither!

 

Amazingly, light sometimes acts like a wave and sometimes like particles - sometimes we have to think of it like waves to explain what happens and sometimes we have to think of it as made of particles.

 

This unusual property is called the wave-particle duality of light.

Adam O. GCSE Maths tutor, GCSE Physics tutor, A Level Maths tutor, A ...

2 years ago

Answered by Adam, an A Level Physics tutor with MyTutor


Still stuck? Get one-to-one help from a personally interviewed subject specialist

117 SUBJECT SPECIALISTS

PremiumJames L. A Level Biology tutor, A Level Chemistry tutor, GCSE Biology...
£26 /hr

James L.

Degree: Medical Sciences (Bachelors) - Exeter University

Subjects offered:Physics, Science+ 4 more

Physics
Science
Maths
Chemistry
Biology
-Personal Statements-

“Hi, I'm James, a Masters student studying Biology. I'm really passionate about science, and I hope i can share some of it with you!”

PremiumShruti V. 13 Plus  Maths tutor, 11 Plus Maths tutor, A Level Maths tu...
£30 /hr

Shruti V.

Degree: Biomedical Engineering (Masters) - Southampton University

Subjects offered:Physics, Maths+ 2 more

Physics
Maths
Chemistry
-Personal Statements-

“I am patient and friendly and strive for a comfortable and fun working environment that also achieves results.”

£20 /hr

Matthew H.

Degree: Physics (Masters) - Liverpool University

Subjects offered:Physics, Maths+ 3 more

Physics
Maths
History
Chemistry
-Personal Statements-

“About Me  I am studying physics at the University of Liverpool and am now in my second year having passed with a first in all my modules last year. I really love all things science and have a real drive to pass on what I know to other...”

About the author

Adam O.

Currently unavailable:

Degree: Physics (Masters) - Oxford, St Hugh's College University

Subjects offered:Physics, Maths+ 1 more

Physics
Maths
Further Mathematics

“Top tutor from the renowned Russell university group, ready to help you improve your grades.”

MyTutor guarantee

|  2 completed tutorials

You may also like...

Other A Level Physics questions

Is Pluto a planet?

If two cars are moving, labelled car A and car B. Car A moves at 15 m/s and B at 10 m/s but car B also accelerated at 2 m/s/s. If the two both travel for ten seconds, which car will travel further?

Explain how a bright line is formed by the diffraction grating at the first order diffraction angle

A student is measuring the acceleration due to gravity, g. They drop a piece of card from rest, from a vertical height of 0.75m above a light gate. The light gate measures the card's speed as it passes to be 3.84 m/s. Calculate an estimate for g.

View A Level Physics tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok