CBSE
A plane glass slab is kept over various colour letters, the letter which appears least raised is :
red
violet
green
blue
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
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 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
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?
The 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
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)
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?
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 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