# Light Waves Flashcards

1
Q

How do you calculate the angle of deviation?

A

The difference between the angles of incidence and refraction.

2
Q

What does the angle of deviation depend on?

A

The difference between the refractive indices of 2 media. The greater the difference, the greater the angle.

3
Q

What is refraction?

A

When the direction of light changes due to a change in the velocity.

4
Q

When does refraction occur?

A

When light travels from one medium to another.

As light travels from a medium from a higher refractive index to a lower (water-air) it bends away from the normal, and vice-versa.

5
Q

What is the refractive index?

A

The ratio of the speed of light in a vacuum to the speed of light in a medium.

n = c/v

6
Q

What is dispersion and when does it occur?

A

It occurs due to refraction when white light passes through a prism.
When this happens, the light is split into all visible light ROYGBIV.

7
Q

What is diffraction? What is the ratio for diffraction?

A

The bending of waves/light when it travels through slits.
This creates interference patterns which can be constructive (bright spot) or destructive (dark spot).

Diffraction = λ/w

8
Q

Explain what happens with diffraction with the ratio of λ/w.

A

As the λ increases, diffraction increases.
As the λ decreases, diffraction decreases.

As the w increases, diffraction decreases.
As the w decreases, diffraction increases.

9
Q

What is polarisation? How does it support light being a wave?

A

Where a transverse wave can only vibrate in 1D.
Light waves are EM waves (electro-magnetic).
Since light can be polarised, it must mean that it’s a transverse wave.

10
Q

Which of the 2 competing models does Young’s Double Slit Experiment support?

A

The wave model.

11
Q

How do the results of Young’s experiment support the wave model?

A

Because an interference is caused by

• Alternating constructive & destructive interference
• There’s diffraction through the two slits

Interference and diffraction are both wave behaviours.

12
Q

Why do the results of the Young’s experiment not support the competing model?

A

If light behaved as a particle, then we’d only expect to see 2 bright spots on the screen rather than an interference pattern.

13
Q

When is light produced?

A

When charged particles accelerate. They consist of an electric field which in turn creates a changing magnetic field. Hence, light is an EM wave.

14
Q

Why are microwaves tuned to a certain frequency?

A

They are tuned to 2.45GHz in order to match the resonant frequency of water. This allows for it to vibrate the water molecules in the food and transfers the energy to the rest of it to heat it up.