Wave Properties

Question 1

How do you use a ripple tank to measure the wavelength of a wave

Answer 1

1. Use a signal generator attatched to a dipper in a ripple tank to create waves in a ripple tank at a set frequency
   - Use a lamp to see the wavelengths on a screen below the tank
   - The distance between each shadow line is a wavelength . Measure the distance between two shadow lines that are 10 wavelengths apart and divide the distance by ten to get an average wavelength
   - Use the equation wave speed= frequency x wavelength to find the speed of a wave
   - This is a good method to use as you can measure the wave speed and length without disturbing the waves

Question 2

What is the law of reflection

Answer 2

The law of reflection states that
Angle of incidence= Angle of refelection

The angle of incidence is the angle between the incoming ray and the normal

The angle of reflection is the angle between the reflected ray and the normal

See diagram

Question 3

What is specular reflection and when does it occur

Answer 3

Specular reflection is when a wave is reflected in a single direction from a perfectly smooth surface

Question 4

What is diffuse reflection and when does it occur

Answer 4

Diffuse reflection occurs when a wave is reflected in many different directions and it happens when the wave is reflected from a rough or uneven boundary

(Angle of incidence still = angle of reflection)

Question 5

What is refraction and when does it occur

Answer 5

Rarefaction occurs when a wave changes direction usually at the boundary between two different materials. The density of the material affects how fast the wave can pass through it. When a wave passes from a more dense material to a less dense material it will gain speed and appear to bend

Question 6

What happens when a wave is refracted and crosses into a more/ less dense material

Answer 6

• When a wave crosses into a more dense material the wave gets slower
• When a wave crosses into a less dense material the wave speeds up

Question 7

How does this affect a ray diagram and how much waves are refracted

Answer 7

If a wave enters a more dense material it will slow down, this causes it to bend towards the normal

If a wave enters a less dense material it will speed up causing it to bend towards the normal

-NOTE when a wave enters a material with a different density its wavelength changes but frequency stays the same