Topic 5a - Refraction Waves

Question 1

What is refraction?

Answer 1

The change in direction of a wave, due to a change in density, causing a change in speed

Question 3

Describe what happens to light as it passes from air into glass

Answer 3

The light refracts as it slows down and changes direction towards the normal

Question 4

Explain how the soldiers walking onto sand from the road explains thr process of refraction

Question 5

What is the critical angle?

Answer 5

Angle of incidence in the denser medium that causes an angle of refraction of 90 degrees in the less dense medium
(As for sin(Theta c) to be less than 1 then the refractive index of n1 must be greater than that of n2

Question 6

A high refractive index means what about the speed of light in one medium compared to another?

Answer 6

Refractive index = speed of light/ speed in the medium
So a high refractive index = a lovw speed in the medium

Question 8

Draw the shape of a convex lens and explains what this lens does to rays of light

Answer 8

Light converges on the principal
Focus

Question 9

Draw the shape of a concave lens and describe what this type of lens does to rays of light

Answer 9

Question 10

Increasing what thing increases the angle of deviation?

Answer 10

Distance of ray from principal axis,as this increases angle of incidence

Question 11

Incident rays which travel parallel to the principal axis converge where?

Answer 11

At the focal point

Question 12

Which rays converge at the focal point of a convex lens

Answer 12

Rays travelling parallel to the principal axis

Question 13

Explain how a convex lens focuses a beam of light travelling parallel to the principal axis

Answer 13

• going from the centre of the lens to the top the angle of incidence on the lens increases
  So the angle of deviation increases
  So all rays cross the principal axis at the principal focus

Question 14

How can you get effectively parallel rays of light incident on objects

Answer 14

Very distant objects emit light rays that can be treated as parallel to the principal axis

Question 15

Thicker lenses have a greater what

Answer 15

Greater refraction - so parallel rays converge closer to the lens

Question 18

If the refraction of a lens is higher than how will this affect the distance of teh focal point from the lens

Answer 18

It decreases the distance

Question 19

What is the principal focus

Answer 19

The point on the principal axis where rays parallel to the principal axis will converge

Question 20

What is the focal length?

Answer 20

The distance between the centre o f the lens and the principal focus

Question 21

Is the focal length negative or positive for converging lenses? And diverging lenses?

Answer 21

Positive, then negative

Question 22

If we view a distant object with a convex lens, where does the image form?

Answer 22

At the focal point

Question 23

Describe the image seen if you view a distant object with a convex lens?

Answer 23

Real, inverted, diminished

Question 24

How do we know if an image is real?

Answer 24

It can be projected on a screen\and it is behind the lens (relative to object)

Question 25

Describe the image formed if you view an object through a lens at a distance less than the focal length?

Answer 25

Magnified, upright, virtual

Question 26

Explain how to estimate the focal length of a convex lens

Answer 26

Measure the distance to the image formed by viewing an object at a distance

Question 27

What is the symbol for a convex lens?

Answer 27

An arrow with the heads pointing outwards

Question 28

What does u mean in the thin lens equation

Answer 28

Distance object to lens

Question 29

What kind of line do you use to draw virtual rays?

Answer 29

Dotted line

Question 30

What is a real image?

Answer 30

Image formed from real light rays converging to a point where the image is formed

Question 31

What is a virtual image

Answer 31

The rays don’t pass through the image position - formed by the apparent divergence of light rays from a. Single point

Question 32

When is no image formed by a convex lens

Answer 32

When the object is the focal length away from the lens

Question 33

When the convex lens is acting as a magnifying glass what kind of rays are forming the image?

Answer 33

Virtual rays

Question 34

Convex lens: if the object distance from lens is greater than focal length what image is formed?

Answer 34

Real, inverted and magnified or diminished

Question 35

What kind of image is formed when the object distance from lens is equal to focal length for a convex lens?

Answer 35

No image

Question 36

What kind of image is formed when the object distance from lens is less than focal length for convex lens

Answer 36

Virtual, upright, magnified

Question 37

What kind of image is always formed by a concave lens

Answer 37

Virtual, diminished, upright

Question 38

Distances to real objects and real images are positive or negative

Answer 38

Positive

Question 39

Distances from lenses to virtual objects and images are positive or negative

Answer 39

Negative

Question 41

If a ray emerges from a medium into the same medium that it was in before it changed mediums - what can we say about the angle of incidence and the angle at which it emerges?

Answer 41

They are equal