Y1 Light

Question 1

What are the properties of an image reflected off of a mirror?

Answer 1

• Upright
• The same size as the object
• The distance from the mirror to the object is the same as the apparent distance from the mirror to the image
• It is laterally inverted
• It is virtual (cannot be formed on a screen)

Question 2

What happens when light is reflected off of a rough surface?

Answer 2

It is diffused (parralel incident rays are reflected in all directions)

Question 3

What is cyan, magenta and yellow light?

Answer 3

They are secondary colours
Cyan: Blue + Green
Magenta: Red + Blue
Yellow: Red + Green

Question 4

What is colour subtraction?

Answer 4

When 2 or more colours are shined on an object such that some are absorbed or get cancelled out
e.g. Cyan + Blue on Red object = Black
Magenta + Yellow on White object = Red

see ZF’s notes for equations

Question 5

What is a filter?

Answer 5

It is a transparent object that absorbs light, only allowing certain colours to pass through
e.g. a red filter absorbs green and blue light, only allowing red light to pass through

Question 6

What is refraction?

Answer 6

The bending of light when it passes from one medium into another due to a change in speed.

Question 7

When does refraction not occur?

Answer 7

When light travels into a medium that has the same refractive index as its previous medium
OR
When light travels along the normal from one medium into the next

Question 8

True/false: when light travels from an optically denser medium to an optically less dense medium, light bends towards the normal.

Answer 8

False
When light slows down, ti bends away from the normal

Question 9

What are concave and convex lenses?

Answer 9

Convex: Converging lens, widest at middle
Concave: Diverging lens, widest at edges

Question 10

What is a focal point?

Answer 10

The points where incident rays travelling parallel to the optical axis converge after passing through a lens; One is present on each side of the lens

Question 11

What is a focal length?

Answer 11

The distance from the center of the lens to either focal point

Question 12

What is an optical/principal axis?

Answer 12

A central horizontal line passing through the center of the lens

Question 13

When should the image distance be negative?

Answer 13

When the image is formed on the same side of the lens as the object, forming a virtual image

Question 14

When should image height be negative?

Answer 14

When the image is inverted, forming a real image

Question 15

When should magnification be negative?

Answer 15

When the image is real and inverted

Question 16

What is the image distance when the object distance is: >2f, =2f, between 2f and f, =f, <f

Answer 16

xₒ > 2f: xᵢ between 2f and f
xₒ = 2f: xᵢ = 2f
xₒ between 2f and f: xᵢ > 2f
xₒ = f: image at infinity
xₒ < f: xᵢ > 2f (same side)

Question 17

What are the 3 principal rays how do you use them?

Answer 17

Ray 1: Parralel to optical axis, bends to pass through focal point
Ray 2: Passes through center of lens, does not bend
Ray 3: Passes through focal point, bends to become parralel to optical axis
The point where the 3 rays converge is where the image forms.

Image to help visualize; rays are numbered from top to bottom

Question 18

How do convex and concave lenses correct vision?

Answer 18

Convex lenses correct far-sightedness by decreasing focal length; Concave lenses correct near-sightedness by increasing it.

Question 19

What wavelengths of light refract less?

Answer 19

Lower wavelengths