Lenses

Question 1

How do lenses form images

Answer 1

By refracting light and changing its direction

Question 2

What are the main 2 types of lenses

Answer 2

Convex

Concave

Question 3

What happens to a convex lens and what does it do to light

Answer 3

It bulges outward

Causes rays of light parallel to axis to be brought together at the principle focus

Question 4

What do concave lenses do and what do they do to light rays

Answer 4

The lens caves inwards

Causes rays of light parallel to axis to spread out

Question 5

What is the axis of a lens

Answer 5

A line passing through the middle of the lens

Question 6

What is the principal focus of a
Convex lens
Concave lens

Answer 6

Convex - rays hitting the lens parallel to axis all meet

Concave - point where rays hitting the lens parallel to axis appear to all come from

Question 7

What is the focal length

Answer 7

The distance form the centre of the lens to the principal focus

Question 8

What are the 3 rules of refraction in a convex lens

Answer 8

Incident ray parrallel to axis refracts through lens and passes through principal focus on otherside
Incident ray passing though the principal focus refracts though lens and travels parallel to axis
Incident ray passing though centre of lens carries on in same direction

Question 9

What are the 3 rules for refraction in concave lens

Answer 9

Incident ray parallel to axis refracts through lens and travels in line with principal focus
Incident ray passing through the lens towards the principal focus refracts through lens and travels parallel to axis
Incident ray passing though centre carries on in the same direction

Question 10

What is a real image

Answer 10

Where the light from the object comes together to form an image on a screen

Question 11

What is a virtual image

Answer 11

The rays are diverging so the light from the object seems to be coming from a completely different place

Question 12

When do you get virtual images

Answer 12

When looking in mirror

Magnifying lens

Question 13

How do you describe an object

Answer 13

How big it it
If it’s upright or inverted relative to object
Real or virtual

Question 14

What type of image does a concave lens always produce

Answer 14

A virtual image

That is upright, smaller and on the same side of lens as the object

Question 15

How do magnifying glasses work

Answer 15

They create a magnified virtual image

Question 16

What can’t you do with a virtual image

Answer 16

You can’t project a virtual image into a screen because the light rays don’t actually come from the place where the image appears to be

Question 17

What is the magnification Formula

Answer 17

Image height / object height

Question 18

What is the range of wavelengths in visible light

Answer 18

400-700 nm

Question 19

What are opaque objects and what colour are they

Answer 19

They do not transmit light
They absorb some wavelengths of light and reflect others
It’s colour depends on which wavelengths of light are most strongly reflected

Question 20

What do opaque objects that aren’t a primary colour reflect

Answer 20

Wavelengths of light corresponding to that colour
Or
Wavelengths of the primary colours that can mix tougher to make that colour

Question 21

What do transparent and translucent objects do with light

Answer 21

They transmit light so it can pass through

Question 22

What are colour filters

Answer 22

They are used to filter out different wavelengths of light so that only certain colours are transmitted and the rest are absorbed

Question 23

What happens if you look at a red hat through a blue colour filter

Answer 23

The hat would appear black because red light is relegated by the hat but it’s not transmitted because the only colour that would be transmiteed would be a
Blue coloured hat