4th Form Waves Flashcards Preview

4.4 2017 > 4th Form Waves > Flashcards

Flashcards in 4th Form Waves Deck (20)
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1
Q

What is the law of reflection?

A

angle of incidence = angle of reflection

2
Q

What is the reflection of sound called?

A

An echo

3
Q

What is an image?

A

A location where multiple rays cross

4
Q

What is a real image?

A

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

5
Q

What is a virtual image?

A

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

6
Q

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

A

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.

7
Q

What is refraction?

A

The bending of light due to a change in speed.

8
Q

Why does refraction occur?

A

A change in speed.

9
Q

What is Snell’s law?

A

n = sin (i) / sin (r)

10
Q

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

A

SHIFT -> SIN -> ANS

11
Q

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

A

Towards the normal.

12
Q

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

A

Away from the normal

13
Q

What is the critical angle?

A

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

14
Q

How can I find the critical angle?

A

Sin (c) = 1 / n

15
Q

What does TIR stand for?

A

Total Internal Reflection

16
Q

When does TIR happen?

A

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

17
Q

What are the applications of TIR?

A

Cat’s eyes, periscopes and optical fibres

18
Q

What is the Doppler effect?

A

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

19
Q

What is the equation for the Doppler effect?

A

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

20
Q

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

A

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.