# PHYSICS : REVISION TEST ON TOPICS OF CLASS XII ---II

The focal lengths for violet, green and red light rays are and  respectively. Which of the following is the true relationship?
An object placed 10 cm in front of a lens has an image 20 cm behind the lens. What is the power of the lens (in dioptres)?
1.5
3.0
– 15.0
+ 15.0
A thin plano-convex lens acts like a concave mirror of focal length 0.2 m when silvered from its plane surface. The refractive index of the material of the lens is 1.5. The radius of curvature of the convex surface of the lens is ____.
0.4 m
0.2 m
0.1 m
0.75 m
At what distance from a convex lens of focal length 30 cm, an object should be placed so that the size of the image be of the object ____.
30 cm
60 cm
15 cm
90 cm
/
The sun makes 0.5o angle on earth surface. Its image is made by convex lens of 50 cm focal length. The diameter of the image is ____.
5 mm
4.36 mm
7 mm
None of the above
If aperture of lens is halved then image is ____.
no effect on size
intensity of image decreases
both A and B
None of the above
A magnifying glass is to be used at the fixed object distance of 1 inch. If it is to produce an erect image magnified 5 times its focal length should be ____.
0.2 inch
0.8 inch
1.25 inch
5 inch
An object is placed 12 cm to the left of a converging lens of focal length 8 cm. Another converging lens of 6 cm focal length is placed at a distance of 30 cm to the right of the first lens. The second lens will produce ____.
no image
a virtual enlarged image
a real enlarged image
a real smaller image
In order to obtain a real image of magnification 2 using a converging lens of focal length 20 cm, where should an object be placed?
50 cm
30 cm
– 50 cm
– 30 cm
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TOPICS: lenses, their focal length, power , microscope

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Kajal Sengupta
Physics 9th to 12 th grade,CIE, Edexcel, AP, IB , CBSE, ICSE
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