Download Lenses, the eye and other applications of light

Lenses, the eye and other applications of light
P3
70 minutes
70 marks
Page 1 of 26
Q1.
(a) Each diagram shows a light ray incident on a glass-air boundary.
The critical angle for glass is 42°.
Which one of the diagrams, A, B, C or D, shows total internal reflection?
Write the correct letter in the box.
(1)
(b)
(i)
Complete the diagram to show the path taken by the light ray as it travels through the
optical fibre.
(2)
(ii)
The diagram shows an endoscope being used by a doctor to look inside a patient’s
stomach. Light travels into the stomach through a bundle of optical fibres.
Page 2 of 26
The following sentences describe how the endoscope allows the doctor to see inside
the patient’s stomach. The sentences are in the wrong order.
Q
Light passes through a bundle of optical fibres into the patient’s stomach.
R
The inside of the stomach reflects some of the light.
S
The optical fibres take the light to an eyepiece.
T
The doctor looks through the eyepiece to see inside the patient’s stomach.
U
The reflected light passes through a second bundle of optical fibres.
Arrange these sentences in the correct order. Start with letter Q.
(3)
(Total 6 marks)
Q2.
The diagram shows a lens being used as a magnifying glass.
(a)
(i)
What type of lens is shown in the diagram?
Draw a circle around your answer.
concave
converging
diverging
(1)
Page 3 of 26
(ii)
Use the equation in the box to calculate the magnification produced by the lens.
The object and image in the diagram have been drawn to full size.
Show clearly how you work out your answer.
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Magnification = ........................................
(2)
(b)
The diagram shows how the image changes when the object has been moved closer to the lens.
Complete the following sentence by drawing a ring around the correct line in the box.
increases
Moving the object closer to the lens
does not change
the magnification produced
decreases
by the lens.
(1)
(Total 4 marks)
Page 4 of 26
Q3.
(a)
The diagrams below show rays of light striking a mirror and a perspex block.
Complete the paths of the three rays of light on the diagrams to show the rays leaving the
mirror and the perspex block.
(4)
(b)
The diagram below shows a beam of light striking a perspex block.
(i)
Continue the paths of the rays AB and CD inside the perspex block.
(ii)
Draw the wavefronts of the beam of light in the perspex.
(iii)
Explain why the beam behaves in the way you have shown.
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(7)
Page 5 of 26
(c)
The diagram below shows a ray of light striking a perspex-air surface from inside the
perspex. The critical angle is 45º.
Draw the path of the ray after it reaches the perspex-air boundary.
(2)
(Total 13 marks)
Q4.
The diagram shows a lens, the position of an object and the position of the image of the
object.
(a)
What type of lens is shown?
........................................................................................................................
(1)
(b)
What is the name of the points, F, shown each side of the lens?
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(1)
(c)
(i)
The image is real and can be put on a screen.
How can you tell from the diagram that the image is real?
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(1)
Page 6 of 26
(ii)
Draw a ring around a word in the box which describes the image produced by the
lens.
inverted
larger
upright
(1)
(d)
A student investigates the relationship between the distance from the object to the lens
and the magnification produced by the lens.
The student’s results are given in the table.
The student did not repeat any measurements.
Distance
in millimetres
Height of object
in millimetres
Height of image
in millimetres
Magnification
produced
40
20
58
2.9
50
20
30
1.5
60
20
20
1.0
70
20
14
0.7
80
20
12
0.6
90
20
10
0.5
The student plots the points for a graph of magnification produced against distance.
(i)
Draw a line of best fit for these points.
(1)
Page 7 of 26
(ii)
Complete the following sentence by drawing a ring around the correct word in the
box.
A line graph has been drawn because both variables are
categoric.
described as being
continuous.
discrete.
(1)
(iii)
Describe the relationship between magnification produced and distance.
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(2)
(Total 8 marks)
Q5.
(a)
(i)
The diagram shows a converging lens being used as a magnifying glass.
On the diagram, use a ruler to draw two rays from the top of the object which show
how and where the image is formed. Represent the image by an arrow drawn at the
correct position.
(3)
Page 8 of 26
(ii)
Use the equation in the box to calculate the magnification produced by the lens.
Show clearly how you work out your answer.
...............................................................................................................
...............................................................................................................
Magnification = ........................................
(2)
(b)
A camera also uses a converging lens to form an image.
Describe how the image formed by the lens in a camera is different from the image
formed by a lens used as a magnifying glass.
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(2)
(Total 7 marks)
Q6.
(a)
The diagram shows the inside of the eye of a person with perfect vision.
Complete the sentence.
The process by which the cornea and lens change the direction of the light is called
...................................................................... .
(1)
Page 9 of 26
(b)
(i)
Not everyone has perfect vision.
A short-sighted person can only clearly see objects which are close.
Light from distant objects meets in front of the retina.
The diagrams show how an additional lens will correct short-sightedness.
Uncorrected vision
Vision corrected with
a diverging lens
The following diagram shows what happens when light from a close object enters the
eye of a long-sighted person.
Light fails to come
to
focus on the retina
What type of additional lens will correct the vision of a long-sighted person?
......................................................................
(1)
(ii)
The additional lens changes the direction of the light before it enters the eye.
Why does this correct the person’s vision?
...............................................................................................................
...............................................................................................................
(1)
Page 10 of 26
(c)
Read this passage from a magazine.
Explain how these glasses are adjusted for a short-sighted person and how this
adjustment allows the person to see distant objects clearly.
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(3)
(Total 6 marks)
Page 11 of 26
Q7.
The diagram shows two lenses, A and B. Two rays of light are shown incident on the lefthand surface of each lens.
Lens A
(a)
Lens B
On the diagram, draw lines to show how the light passes through each lens into the region
within the dotted lines.
(3)
(b)
A student has short sight because his eyeball is too long. This produces a blurred image.
To be able to see clearly, the student wears glasses.
Which lens, A or B, should be used in the student’s glasses?
Write your answer in the box.
Explain how your chosen lens corrects the student’s short sight.
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(5)
(c)
It is sometimes possible to correct short sight by having the cornea of the eye reshaped.
What device is used by a surgeon to reshape the cornea?
Draw a ring around one answer.
drill
laser
scalpel
(1)
(Total 9 marks)
Page 12 of 26
Q8.
(a)
(i)
The diagram shows a section through a human eye.
Use words from the box to label the diagram.
Ciliary muscle
Cornea
Iris
Lens
Pupil
Retina
(4)
Page 13 of 26
(ii)
In this question you will be assessed on using good English, organising information
clearly and using specialist terms where appropriate.
Describe the functions of the ciliary muscle and the iris.
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(6)
(b)
Draw a ring around the correct answer to complete the sentence.
eyeball being too long.
Long sight can be caused by the
eyeball being too short.
cornea being irregularly shaped.
(1)
Page 14 of 26
(c)
The diagram shows how a convex lens forms an image of an object.
This diagram is not drawn to scale.
(i)
Which two words describe the image?
Draw a ring around each correct answer.
diminished
inverted
magnified
real
upright
(2)
(ii)
The object is 4 cm from the lens. The lens has a focal length of 12 cm.
Calculate the image distance.
Use the correct equation from Section B of the Physics Equations Sheet.
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Image distance = ................................ cm
(3)
(d)
What does a minus sign for an image distance tell us about the nature of the image?
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(1)
(Total 17 marks)
Page 15 of 26
M1.
(a)
D
1
(b)
(i)
total internal reflection shown
1
2 or 3 reflections only
1
(ii)
RUST
correct order
allow 2 marks for two in correct place
allow 1 mark for one in correct place
3
[6]
M2.
(a)
(i)
converging
1
(ii)
(x) 2
allow 1 mark for correct substitution
ie 10/5 or 20/10 or 2/1
ignore any units
2
(b)
decreases
1
[4]
M3.
(a) Reflection correct
Normal incidence correct in and out
Correct refraction in
Parallel ray out
each for 1 mark
4
(b)
(i)
Each ray correctly refracted in
1+1=2
7
(ii)
Wavefronts perp sides
Wavefronts closer
(Cannot score wavefront marks if refracted rays clearly wrong)
(iii)
Speed reduces
Starting at B
Then D
each for 1 mark
Page 16 of 26
(c)
TIR correct
gets 2 marks
Else rough reflection
gets 1 mark
2
[13]
M4.
(a)
converging (lens)
accept ‘convex (lens)’
accept biconvex
1
(b)
(principal) foci
accept ‘focus’ / ‘focuses’ / ‘focis’
focal point(s)
1
(c)
(i)
formed where (real) rays (of light) intersect / meet / cross
accept rays (of light) pass through the image
accept ‘image is on the opposite side (of the lens to the object)’
accept (construction) lines cross over
a response relating to a screen or similar is neutral
lines are solid and not dotted is neutral
1
(ii)
inverted
accept any unambiguous correct indication
1
(d)
(i)
smooth curve which matches the points
judge by eye but do not accept point to point by ruler or otherwise
1
(ii)
continuous
1
(iii)
as distance increases, magnification decreases
accept negative correlation
a statement ‘inversely proportional’ is incorrect and limits
maximum mark for this part question to 1
1
further detail eg magnification falls steeply between 40 and 50 cm
or
magnification begins to level out after / at 70 cm
1
[8]
Page 17 of 26
M5.
(a)
(i)
two correct rays drawn
1 mark for each correct ray
•
ray parallel to axis from top of object and refracted through focus
and traced back beyond object
•
ray through centre of lens and traced back beyond object
•
ray joining top of object to focus on left of lens taken to the lens
refracted parallel to axis and traced back parallel to axis beyond object
2
an arrow showing the position and correct orientation of the image for their rays
to gain this mark, the arrow must go from the intersection of the
traced-back rays to the axis and the image must be on the same
side of the lens as the object and above the axis
1
(ii)
(x) 3.0
accept 3.0 to 3.5 inclusive
or
correctly calculated
allow 1 mark for correct substitution into equation using their figures
ignore any units
2
Page 18 of 26
(b)
any two from:
in a camera the image is:
•
real not virtual
•
inverted and not upright
accept upside down for inverted
•
diminished and not magnified
accept smaller and bigger
accept converse answers but it must be clear the direction of the
comparison
both parts of each marking point are required
2
[7]
M6.
(a)
refraction
1
(b)
(i)
converging
accept convex
1
(ii)
cause the light (rays) to meet on / focus at retina / back of eye
do not accept hit the retina only
1
(c)
silicone is removed from the lens(es)
1
lens(es) thinner in / at the middle (than at the edge)
or
lens(es) became concave / diverging
1
diverges(s) the light which (now) meets / focuses at the retina / back of the eye
1
[6]
M7.
(a)
Lens A both rays converging on other side of lens
1
Lens B both rays diverging on other side of lens
1
Either refraction at both surfaces within lens or refraction at vertical
line through midpoint
1
Page 19 of 26
(b)
(Lens B)
parallel rays (from a distant object) are focused in front of the retina
1
Lens B diverges the ray before entering the eye
1
hence rays appear to come from the far point of the student’s eye
1
and are focused on the retina
1
producing a sharp image
1
(c)
laser
1
[9]
M8.
(a)
(i)
award 1 mark for each correct label
4
Page 20 of 26
(ii)
Marks awarded for this answer will be determined by the quality of
communication (QoC) as well as the standard of the scientific response.
Examiners should apply a best−fit approach to the marking.
0 marks
No relevant content.
Level 1 (1 − 2 marks)
There is a basic description of at least one of either ciliary muscle or iris in
terms of function.
Level 2 (3 − 4 marks)
There is a clear description of the function of ciliary muscle and iris
or
a full, detailed description of either ciliary muscle or iris.
Level 3 (5 − 6 marks)
There are clear and detailed descriptions of the functions of both ciliary muscle
and iris.
examples of the physics points made in the response:
Ciliary muscle:
•
changes the shape of the lens
•
relaxes to flatten lens
•
allowing light to be focused from distance
•
contracts to round lens
•
allowing light to be focused from close objects
Iris:
•
•
•
•
•
•
controls the amount of light entering the eye
expands / relaxes making pupil smaller
in bright light
contracts making pupil larger
in low light
helps protects the retina (in bright light)
6
(b)
eyeball being too short
1
(c)
(i)
magnified
1
upright
1
(ii)
v = −6(cm)
max 2 marks if no minus sign
6(cm) gains 2 marks
1/v = 1/12 − 1/4 = −1/6
gains 2 marks
1/12 = 1/4 + 1/v
gains 1 mark
−5.99(cm)
using decimals gains 3 marks
3
Page 21 of 26
(d)
it is virtual
1
[17]
Page 22 of 26
E2.
(a)
(ii)
(b)
E4.
(i)
Nearly 62% of candidates knew that the diagram showed a converging lens.
Those candidates able to read the diagram found that the calculation very simple.
However a significant proportion of candidates multiplied their two numbers rather
than divide them and therefore gained no marks, this was despite being given the
equation.
Although the information required was provided in the diagram, only 58% of candidates
correctly identified the effect on the image of moving the object closer to the lens.
(a)
Just over half of the candidates could identify the type of lens shown in the diagram.
(b)
Just over three-fifths of candidates were able to correctly name the points labelled F.
(c)
(i)
Explaining how a diagram shows whether an image is real or virtual continues to be
a problem. Many candidates mention ‘in front’ or ‘behind’ the lens without identifying
what they mean. Candidates need to state whether it is the same or opposite side of
the lens to the object. A number of candidates negated any answer by mentioning
reflections and / or mirrors.
(ii)
Although just over three quarters of candidates scored this mark, it is surprising that
most of the remainder thought that the image was upright.
(i)
The response to drawing the line of best fit on given plotted points was extremely
disappointing. Many candidates ignored the point at (40,2.9). The majority of
candidates tried to draw a straight line through an obvious curve while others joined
up the points with a ruler. Only a third of candidates drew an acceptable curve
through the points.
(ii)
Just over two-thirds of candidates gave the correct answer to this part question.
(iii)
A large majority of candidates managed to give the basic relationship linking
magnification and distance but a very small number of candidates gained the second
mark by giving more detail.
(d)
Page 23 of 26
E5.
(a)
(i)
Although over 37% of candidates gained all three marks, 50% of candidates
scored zero!
Those scoring zero clearly had no idea how to draw a ray diagram for a converging
lens used as a magnifying glass.
(ii)
(b)
E6.
(c)
E8.
Again poorly answered with 50% of candidates scoring zero. Many candidates failed to
gain any marks as there was no comparison made between the camera and the
magnifying glass.
(a)
(b)
Many candidates knew how to use the magnification equation and even candidates
that had not scored any marks in part (a)(i) were able to gain these two marks
through ‘error carried forward’.
Just over three quarters of candidates gained this mark.
(i)
Just under nine tenths of candidates gained this mark.
(ii)
Only two thirds of candidates gained this mark. Some candidates described the lens
as reflecting the light into the eye. A number of responses were too vague
eg‘improving eyesight’, and did not address the physics principles.
Just over half of candidates gained either 2 or 3 marks. Many candidates did not make it
explicit that the rays spread out/diverge/move further apart before refraction by the
cornea/lens of the eye to focus directly on the retina.
(a)
(ii)
(i)
Nearly three-quarters of students could successfully identify parts of the human
eye. Almost all students gained at least one mark.
In the Quality of Communication question most students were able to describe the
functions of the ciliary muscle and the iris.
A few students linked the action of the ciliary muscle to an effect on the iris rather
than the lens. There was some confusion about how the change in shape of the lens
allowed objects at different distances to be focussed often because the terms ‘fatten’
and flatten’ were used. Some students are not clear concerning the effects of
relaxing and contracting on the size of the lens and the pupil.
A quarter of students scored four or more marks out of six.
Page 24 of 26
(b)
Three-quarters of students knew that long sight can be caused by the eyeball being too
short.
(c)
(i)
Less than three-quarters of students identified the image in the ray diagram as being
magnified and upright.
(ii)
More than half of the students gained full marks for a calculation using the lens
formula that required a minus sign in the answer. Most of the remaining students
forgot to invert the value for the final answer.
(d)
Most students knew that a minus sign meant that the image was virtual.
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