A convex lens and a concave lens, each having same focal length of 25 cm, are put in contact to form a combination of lenses. The power in diopters of the combination is
infinite
One face of a rectangular glass plate 6 cm thick is silvered. An object held 8 cm in front of the first face, forms an image 12 cm behind the silvered face. The refractive index of the glass is
0.4
0.8
The focal lengths of a converging lens measured for violet, green and red colours are fV,fG,fR respectively. We will find
fG > fR
fV < fR
fV > fR
fV = fR
Pick out the longest wavelength from the following types of radiations.
Blue light
Gamma rays
X-rays
Red light
Interference is possible in
light waves only
sound waves only
Both light and sound waves
Neither light nor sound waves
Angle of deviation () by a prism (refractive index = μ, and supposing the angle of prism A to be small) can be given by
Ray optics is valid, when characteristic dimensions are
of the same order as the wavelength of light
much smaller than the wavelength of light
of the order of one millimetre
much larger than the wavelength of light
A man is 6 ft tall. In order to see his entire image, he requires a plane mirror of minimum length equal to
6 ft
12 ft
2 ft
3 ft
A beam of monochromatic light is refracted from vacuum into a medium of refractive index 1.5. The wavelength of refracted light will be
dependent on intensity of refracted light
same
smaller
larger
A transparent cube contains a small air bubble. Its apparent distance is 2 cm when seen through one face and 5 cm when seen through other face. If the refractive index of the material of the cube is 1.5, the real length of the edge of cube must be
7 cm
7.5 cm
10.5cm