Waves

Question 1

what do waves do?

Answer 1

Waves transfer energy from one place to another without transferring matter. Wave motion can be shown by the vibrations of a spring or by water waves.

Question 2

How do we calculate wave speed?

Answer 2

We can calculate speed by multiplying the frequency of the wave by its wavelength.

Question 3

What is the unit for wave speed?

Answer 3

metres per second (m/s)

Question 4

What happens when waves travel from one medium to another?

Answer 4

Their speed and wavelength change but their frequency stays the same.

Question 5

What is speed directly proportional to?

Answer 5

wavelength

Question 6

Why does the frequency of a wave not change?

Answer 6

The source is producing the same number of oscillations (vibrations) per second.

Question 7

What does transmission involve?

Answer 7

• Waves carry on travelling through a new material

- This often leads to refraction.

Question 8

What does absorption involve?

Answer 8

• When waves meet some materials, the energy is absorbed by the materials.
• For example, when light falls on a matt black surface, most of the energy is absorbed.

Question 9

What does refraction involve?

Answer 9

• A wave’s speed can change when moving from one medium to another.
• If the wave crosses to the new medium at an angle (not 90 degrees), the change in the wave’s speed will cause the direction of the wave’s motion to change and the wave will appear to bend.
• This is called refraction.

Question 10

What does reflection involve?

Answer 10

• Reflection happens when a wave hits a flat surface (plane) and bounces off.

Question 11

What is the angle of incidence?

Answer 11

• The angle between the incident (incoming) light ray and the normal.
• The normal is a line at 90 degrees to the plane.

Question 12

What is the angle of reflection?

Answer 12

The angle between the reflected light ray and the normal.

Question 13

What does the law of reflection state?

Answer 13

The angle of incidence = the angle of reflection

Question 14

What happens when a light enters a more optically dense medium?

Answer 14

It is refracted closer to the normal and the angle of refraction is smaller.

Question 15

What is internal reflection?

Answer 15

Light speeds up when entering a less optically dense medium. When this happens, some light is refracted and some light is reflected.

Question 16

What is total internal reflection?

Answer 16

If the angle of incidence is the same as the critical angle, the light will travel along the boundary of the 2 medians. If the angle of incidence exceeds the critical angle, then all the light will be reflected. This is called total internal reflection.

Question 17

What will happen to the wave if the light enters a less optically dense material?

Answer 17

It will speed up