CBSE
Multiple Choice QuestionsThe time taken by light to pass through 4 mm thick glass slab of refractive index 1.5 will be : (velocity of light in air= 3 x 108 m/s)
8 × 10-11 s
2 × 10-11 s
8 × 10-8 s
2 × 10-8 s
A person who can see things most clearly at a distance of 10 cm, requires spectacles to enable to see clearly things at a distance of 30 cm. What should be the focal length of the spectacles?
15 cm (Concave)
15 cm (convex)
10 cm
0
If a convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together, what will be their resultant power?
+0.65 D
-0.65 D
+0.75 D
-0.75 D
A short linear object of length b lies along the axis of a concave mirror of focal length ' f ' at a distance 'u' from the pole of the mirror, what is the size of image?
A convex lens forms a full image of the object on a screen. If half of the lens is covered with an opaque object, then :
the image disappears
half of the image is seen
full image is seen and of same intensity
full image is seen and of decreased intensity
The refractive index of the material of the prism and liquid are 1.56 and 1.32 respectively. What will be the value of 0 for the following refraction?
What should be the minimum value of refractive index of the material of the prism for the reflections to take place as shown in the figure?
1.7
1.4
1.2
2.7
A lens acts as converging in air and diverging when immersed in water. Then, refractive index of lens is :
equal to unity
below 1.33
greater than 1.33
less than unity
A plane glass slab is kept over various colour letters, the letter which appears least raised is :
red
violet
green
blue
1f the focal length of a lens of a camera is 5f and that of another is 2.5f, what is the time of exposure for the second, if for the first one is ? (where f is focal length / unit aperture)
