Question 1 :
To increase both the resolving power and&#160;magnifying power of a telescope<br/>

Question 4 :
A biprism arrangement in air is immersed completely in a liquid. The fringe width

Question 5 :
If the apertature of a telescope is decreased the resolving power will

Question 6 :
Which of the following properties shows that light is a transverse wave?

Question 7 :
The diameter of objective of a telescope is $1m$. Its resolving limit for the light of wavelength $4538\overset {\circ}{A}$, will be :

Question 8 :
When monochromatic light is replaced by white light in Fresnel's biprism arrangement, the central fringe is

Question 9 :
A beam of light is incident on a liquid of refractive&#160;index 1.40. The reflected rays are completely&#160;polarized. The angle of refraction of the beam&#160;is ($\tan 54.5^{\circ}=1.4$):<br/>

Question 10 :
The bending of light near the edges of an obstacle and spreading into the region of geometrical shadow is called ___________.

Question 11 :
In Young's double-slit experiment, the two slit act as coherent sources of equal amplitude $ A $ and of wavelength $\lambda$. In another experiment with the same setup, the two slits are sources of equal amplitude $A$ and wavelength $\lambda$, but are incoherent. The ratio of intensity of light at the mid-point of the screen is the first case to that in the second case is

Question 12 :
If the source of light used in a Young's double slit experiment is changed from red to violet,

Question 13 :
In Young's double slit experiment the slit separation is $0.5\ m$ from the slits. Distance between the screen and slit is $0.454\ mm$ For a monochromatic light of wavelengths $500\ nm$, the distance of $3^{rd}$ maxima from $2^{nd}$ maxima on the other side is

Question 14 :
In the double slit experiment, the distance between two slits is $0.6mm$ and these are illuminated with light of wavelength $4800A^o$. The angular width of dark fringes on the screen distant $120cm$ from slits will be

Question 15 :
A CD(Compact disc ) is read from the bottom by a semiconductor laser with wavelength $700nm$ passes through a plastic substrate of refractive index $1.8$. When the beam encounters $0$ pit, part of the beam is reflected from the pit and part from the flat region. These two beams interfere with each other. What must be the minimum depth of the pit, So that part of the beam reflected from the pit and part reflected from the flat surface cancel out? (This cancellation allows the player to recognize beginning and end of a pit).

Question 16 :
Calculate the limit of resolution of a telescope objective having a diameter of 200 cm, if it has to detect light of wavelength 500 nm coming from a star ; -

Question 17 :
The objective lens of an optical instrument is an achromat combination with a focal length of $90\&#160; cm$. The two lenses possess dispersive powers $0.024$ and $0.036$ respectively and are in contact with each other. Then their focal lengths are:

Question 18 :
An astronomical telescope, consists of two thin lenses set $36 cm$ a part and has a magnifying power $8$. Calculate the focal length of the lenses.

Question 19 :
Two polarizers have their axes inclined at&#160;$\displaystyle { 45 }^{ \circ &#160;}$ to each other. If unpolarized light of intensity&#160;$\displaystyle { I }$ is incident on the first poilarizer, then the intensity of transmitted light through second polarizer is:

Question 20 :
In a Fresnel's biprism experiment using sodium light, fringe widths of $195$ <br> $\mu$m are obtained at a distance of $1.0\ m$ from the slit . A convex lens is then put between the observer and prism so as to give the image of the source at a distance of $1.0\ m$ from the slit . The distance apart of the images is found to be $0.7\ cm$, the lens being $30\ cm$ from the slit . Calculate the wavelength of the sodium light used.&#160;