Light travels through a glass plate of thickness t and refractive index μ. If c is the speed of light in vacuum the time taken by light to travel this thickness of glass is :
μtc
tc/μ
t/μc
μt/c
An astronomical telescope of ten fold angular magnification has a length of 44 cm. The focal length of the objective is :
440 cm
44 cm
40 cm
4 cm
2 convex lenses
2 concave lenses
1 convex, 1 concave lens
1 convex and 1 plane mirror
A lens is placed between a source of light and a wall. It forms images of area A1 and A2 on the wall, for its two different positions the area of the source of light is :
Interference is possible in
light waves only
sound waves only
Both light and sound waves
Neither light nor sound waves
Rainbows are formed by
reflection and diffraction
refraction and scattering
dispersion and total internal reflection
interference only
Which of the following phenomenon is not explained by Huygen's construction of wavefront?
Refraction
Reflection
Diffraction
Origin of spectra
If two mirrors are kept inclined at 60° to each other and a body is placed at the middle, then total number of images formed is :
Six
Five
Four
Three
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
1.2
1.6
If fv and fn are the focal lengths of a convex lens for violet ad red light respectively and FV and FR are the focal lengths of concave lens for violet and red light respectively, then we have :
fV < fR and FV > FR
fV < fR and FV < FR
fV > fR and FV > FR
fV > fR and FV < FR
