Young's Double Slit

Question 1

What does the light need to be in order for the experiment to work?

Answer 1

Coherent and monochromatic.
Coherent when frequency and wave form are identical.

Question 2

What size should the slit be in order to be the most effective?

Answer 2

Same as the wave length, in order to be diffracted and produce light that acts like two sources.

Question 3

What will you get on the screen?

Answer 3

Light and dark fringes, depending on wether it is constructive or destructive interference happening.

Question 4

What does
x
a
D

stand for?

Answer 4

x=fringe spacing
a=spacing btwn slits
D=distance btwn slits and screen

Question 5

What is Young’s Double Slit formula? When does it work?

Answer 5

x= (λD)/a

All waves when a<D

Question 6

What did Young’s Double Slit experiment show?

Answer 6

Light could both diffract and interfere.
Light was a wave (not a particle like Newton believed) as interference can occur.

Question 7

What is constructive interference?

Answer 7

When two waves are in phase, resultant wave’s displacement at each point is increased.

Question 8

What is destructive interference?

Answer 8

Two waves are in anti-phase, resultant wave’s displacement at all points is 0.

Question 9

Conditions needed for constructive interference?

Answer 9

• Even half multiples of λ path difference.
• Phase difference of even π multiples.

Also known as maxima.

Question 10

Conditions needed for destructive interference?

Answer 10

• Odd half multiples of λ path difference.
• Phase difference of odd π multiples.

Also known as minima.

Question 11

What is the principle of superposition?

Answer 11

“Resultant displacement at a point where similar waves from several sources cross is the vector sum of the individual displacement.”