4th Form Waves

Question 1

What is the law of reflection?

Answer 1

angle of incidence = angle of reflection

Question 2

What is the reflection of sound called?

Answer 2

An echo

Question 3

What is an image?

Answer 3

A location where multiple rays cross

Question 4

What is a real image?

Answer 4

An image where the object is actually located at the point where the rays cross.

Question 5

What is a virtual image?

Answer 5

An image where the object is NOT actually located at the point where the rays cross.

Question 6

How can I find the location of a virtual image in the mirror?

Answer 6

Draw ANY two rays from the object, to the mirror.
Draw on the normal at the points the rays hit the mirror..
Draw on the reflected rays.
Carry the reflected rays back into the mirror. Where they cross, the virtual image is.

Question 7

What is refraction?

Answer 7

The bending of light due to a change in speed.

Question 8

Why does refraction occur?

Answer 8

A change in speed.

Question 9

What is Snell’s law?

Answer 9

n = sin (i) / sin (r)

Question 10

How do I “undo” the sin function on my calculator?

Answer 10

SHIFT -> SIN -> ANS

Question 11

If light moves from air to glass, which way does it bend?

Answer 11

Towards the normal.

Question 12

If light moves from glass to air, which way does it bend?

Answer 12

Away from the normal

Question 13

What is the critical angle?

Answer 13

The angle of incidence, inside the material, that causes an angle of refraction of 90 degrees.

Question 14

How can I find the critical angle?

Answer 14

Sin (c) = 1 / n

Question 15

What does TIR stand for?

Answer 15

Total Internal Reflection

Question 16

When does TIR happen?

Answer 16

When the angle of incidence is greater than the critical angle.

Question 17

What are the applications of TIR?

Answer 17

Cat’s eyes, periscopes and optical fibres

Question 18

What is the Doppler effect?

Answer 18

The increase or decrease of the observed wavelength of a wave due to the relative velocity between the observer and the source.

Question 19

What is the equation for the Doppler effect?

Answer 19

Change in wavelength / wavelength = Speed of object / Speed of the wave

Question 20

Describe an experiment to find the refractive index of a piece of glass.

Answer 20

Draw around the glass block on a piece of paper.
Measure and mark on the normal at a point on the glass block.
Measure and mark on multiple angles of incidence to the normal you have marked.
Replace the block, use a ray box to shine ray of light down the lines you have marked.
Use a pencil to mark where the rays exit the box.
Measure the angles of refraction.
Plot the sin of the angles of incidence against the sin of the angles of refraction and find the gradient - this gradient is the refractive index.