Two lenses of power –15 D and +5 D are in
contact with each other. The focal length of the
combination is
+10cm
-20cm
-10cm
+20cm
The refractive index of glass is 1.520 for red light and 1.525 for blue light. Let D1 and D2 be an of minimum deviation for red and blue light respectively in a prism of this glass. Then
D1>D2
D1<D2
D1=D2
D1 can be less than or greater than depending upon the angle of prism
A monochromatic light is incident at a certain angle on an equilateral triangular prism and suffers minimum deviation. If the refractive index of the material of the prism is , then the angle of incidence is:
In a double-slit experiment, green light (5303 ) falls on a double slit having a separation of 19.44 and a width of 4.05 . The number of bright fringes between the first and the second diffraction minima is :
04
10
09
05
An object is at distance of 20m from a convex lens of focal length 0.3m. The lens forms an image of the object moves away from the lens at a speed of 5m/s, the speed and direction of the image will be:
3.22 X 10^{-3} m/s towards the lens
towards the lens
away from the lens
away from the lens
The variation of refractive index of crown glass thin prism with wavelength of the incident light is shown. Which of the following graphs is the correct one, if D_{m} is the angle of minimum deviation?
In a Young's double slit experiment, the path difference , at a certain point on the screen between two interfering waves is of the wavelength. The ratio of the intensity at this point to that at the centre of a bright fringe is close to:
0.80
0.94
0.85
0.74
Formation of real image using a biconvex lens is shown below :
If the whole set up is immersed in water without disturbing the object and the screen positions , what will one observe on the screen ?
Erect real image
Image disappears
Magnified image
No change
A plano-convex lens (focal length f_{2} , refractive index , radius of curvature R ) fits exactly into a plano-concave lens ( focal length f_{1} , refractive index , radius of curvature R ) . Their plane surfaces are parallel to each other. Then , the focal length of the combination will be :
f_{1} + f_{2}
f_{1} - f_{2}
The eye can be regarded as a single refracting surface. The radius of curvature of this surface is equal to that of cornea (7.8mm) . This surface separates two media of refractive indices 1 and 1.34. Calculate the distance from the refracting surface at which a parallel beam of light will come to focus.
Consider a Young's double slit experiment as shown in figure. What should be the slit sepration d in terms of wavelength such that the first minima occurs directly in front of the slit (S_{1})?
A plano lens of refractive index and focal length is kept in contact with another plano concave lens of refractive index and focal length . If the radius of curvature of their spherical faces is R each and then and are related as:
In a young's double slit experiment with slit sepration 0.1mm, one observes a bright fringe at angle rad by using light of wavelength . When the light of wavelength is used a bright fringe is seen at the same angle in the same set up. Given that and are in visible range (380nm to 740nm), their values are:
625 nm, 500nm
380 nm, 525 nm
380 nm, 500 nm
400 nm, 500 nm
Two plane mirrors are inclined to each other such that a ray of light incident on the first mirror (M_{1}) and parallel to the second mirror (M_{2}) is finally reflect from the second mirror (M_{2}) parallel to the first mirror (M_{1}). The angle between the two mirrors will be:
In a Young's double slit experiment, the slits are placed 0.320 mm apart. Light of wavelength = 500nm is incident on the slits. The total number of bright fringes that are observed in the angular range is:
320
321
640
641
A point source of light, S is placed at a distance L in front of the centre of plane mirror of width d which is hanging vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror., at a distance 2L as shown below . The distance over which the man can see the image of the light source in the mirror is :
3d
d
2d
What is the position and nature of image formed by lens combination shown in figure ? (f_{1}, f_{2} are focal lengths )
40 cm from point B at right; real
from point B at right; real
70 cm from point B at right; real
70 cm from point B at left; virtual
Consider a tank made of glass (refractive index 1.5) with a thick bottom. It is filled with a liquid of refractive index . A student finds that, irrespective of what the incident angle (see figure) is for a beam of light entering the liquid,the light reflected from the liquidglass interface is never completely polarized. For this to happen,the minimum value of is :
Two coherent sources produce waves of different intensities which interfere. After interference, the ratio of the maximum intensity to the minimum intensity is 16. The intensity of the waves are in the ratio:
16 : 9
25 : 9
4 : 1
5 : 3
A convex lens is put 10cm from a light source and it makes sharp images on a screen, kept 10 cm from the lens. Now a glass block (refractive index 1.5) of 1.5 cm thickness is placed in contact with the light source. To get the sharp image again, the screen is shifted by a distance d. Then d is:
11 cm away from the lens
0
0.55 cm towards the lens
0.55 cm away from the lens