Page 12 - 1202 Question Bank Physics Form 4

(c) Why is an image formed by a parabolic mirror sharper than the image of the same object formed by a
concave spherical mirror? HOTS Analysing [3 marks]

Section B
Answer all questions.

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6. (a) In Diagram 6, a real inverted image I of an object O is formed by a particular lens (not shown); the
object–image separation is d = 60.0 cm, measured along the central axis of the lens. The image is just
half the size of the object.
O

Lens here Axis

I
d

Diagram 6
(i) What kind of lens must be used to produce this image?
(ii) How far from the object must the lens be placed?

(iii) What is the focal length of the lens?
(iv) What is the other position of lens that can be used to produce a magnified image? Explain your
answers clearly. HOTS Analysing [8 marks]
(b) A compound microscope contains an objective lens and an eyepiece lens. The focal length of the
objective lens is f and the focal length of the eyepiece lens is f .
o e
You are assigned to study the suitable ways to build a compound microscope with maximum
magnification. Table 1 shows various arrangement for the lenses.
Table 1
Aspect Distance between the
Object distance, Comparison Distance between image formed by the
u from the objective lens
o of f and f objective lens and the
objective lens o e and eyepiece, d
Arrangement eyepiece, u
i
W u , f f , f d . (f + f ) u , f
o o o e o e i e
X u . 2f f . f d = (f + f ) u . f
o o o e o e i e
Y f , u , 2 f f , f d . (f + f ) u , f
o o o o e o e i e
Z u = f f . f d = (f + f ) u = f
o o o e o e i e
(i) Choose the most suitable arrangement and provide reasons for your choice. HOTS Evaluating
[10 marks]
(ii) Apart of the aspects given in Table 1, suggest another one factor for better quality of compound
microscope. Give a reason. HOTS Creating [2 marks]
102 Question 5:
SOS TIP (c) All parallel rays converge at a parabolic mirror’s focal point. The focal point is sharp. SOS TIP
Question 6:
(b) The refractive indices of the objective lens and eyepiece may affect the design of the microscope. The range of wavelengths for the light source also can
affect the quality of image formed.

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