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HKAL Physics : Part 3 Waves
Chapter 12 Optical Instrument Quiz 1
Name :
Class :
(
Marks :
1.
C.
3
D.
)
/ 13
30
3.
v2
v1
M2
M1
M
L
i
I
Light travels in media M1 an M2 with
speeds v1 and v2 respectively. When light
travelling from medium M1 strikes a
boundary between the two media with
angle of incidence i, it suffers total internal
3 cm
3 cm
6 cm
3 cm
A converging light beam is directed
towards a convex mirror M. The reflected
reflection. This indicates that
(1) v1 is less than v2.
(2) sin i is greater than v2/v1.
(3) sin i is greater than v1/v2.
A. (1) only
B. (3) only
C. (1) and (3) only
D. (2) and (3) only
beam then passes through a convex lens L
and forms an image at I. Which of the
following about the focal lengths of M and
L is correct ?
focal length of M focal length of L
A.
more than 3 cm
1.5 cm
B.
less than 3 cm
1.5 cm
C.
less than 3 cm
3 cm
D.
more than 3 cm
3 cm
2.
10 cm
object
A converging lens of focal length 10 cm is
used as a magnifying glass with the final
image at infinity. If the least distance of
distinct vision is 30 cm, the angular
5.
4.
A simple two-convex lens refracting
telescope has a magnifying power of 15
when the telescope is in normal
adjustment. The focal length of the
objective is 0.80 m. The separation
between the objective and the eye piece is
A. 0.05 m.
B. 0.75 m.
C. 0.85 m.
D. 12.8 m.
magnification achieved is
A. 1
B. 2
A student has constructed a refracting telescope as shown in Figure 5.1. The focal lengths of
the objective and the eyepiece are 50 cm and 18 cm respectively.
(a) With the telescope in normal adjustment, find
(i) the separation between the two lenses; and
(ii) the angular magnification when viewing a distant building.
(2 marks)
(b) The student now uses the telescope to view a small piece of newspaper, 4 cm × 4 cm,
HKAL Chapter 12 Optical Instrument Quiz 1
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fixed to a notice-board 1.6 m away from the objective. He then adjusts the position of the
eyepiece such that the final image is formed at infinity.
4 cm
objective
eyepiece
4 cm
1.6 m
Figure 5.1
(i)
On the attached graph paper, complete the ray paths P and Q as they pass through the
telescope, showing how the final image is formed at infinity. The piece of newspaper,
represented by AB, and the objective are already drawn on the graph paper. Label the
positions of the first image of the piece of newspaper and the eyepiece clearly on the
diagram. (Horizontal scale : 1 to 20 ; Vertical scale : 1 to 1)
objective
P
A
(3 marks)
1 cm
20 cm
Fo
Fo
B
Q
(ii) Find the height of the first image and the separation of the objective and the eyepiece.
(2 marks)
(iii) What is the angular magnification in this case ? (Assume that when the piece of
newspaper is observed with an unaided eye, the distance between the piece of
newspaper and the eye remains unchanged.)
(2 marks)
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HKAL Physics : Part 3 Waves
Chapter 12 Optical Instrument Quiz 1 (KEY)
Name :
Class :
(
Marks :
)
/ 13
1 – 4 : CCAC,
5.
(a) (i) 68 cm
(ii) 2.78
(b) (i)
11
11
33
objective
P
A
1 cm
20 cm
Fo
Fo
B
I1
Q
eyepiece
(ii) Height of the first image (I1) = 1.8 cm
Separation of the objective and the eyepiece = 0.9 m
1
12
1.8cm
18cm
(iii)
4cm
1
tan
(1.6  0.9)m
1
tan 1
= 6.23
HKAL Chapter 12 Optical Instrument Quiz 1
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