Power of a lens is - 4D and for the second lens,power is + 2D.The total power for the two in contact is
6 D
-6 D
-2 D
-8 D
The sideways reversal of image by plane mirror is:
Lateral inversion
Parallax
Optical illusion
Optotune
What type of lens will form when a tumbler is filled with water?
Bi convex
Concavoconvex
Plano convex
Biconcave
A man is using concave mirror for shaving.If his face is 20 cm from the mirror having magnification 2,what will be the radius of curvature of the mirror?
60 cm
80 cm
50 cm
40 cm
If R is the radius of curvature of a spherical mirror and f is its focal length,then :
R = f
R = 2f
R = f/2
R = 3f
A virtual image is one which
can be taken on a screen
cannot be taken on a screen
sometimes can be and sometimes cannot be taken on a screen
is formed only by a concave mirror
A concave mirror cannot be used as :
a magnifying mirror
a torch reflector
a dentist's mirror
a rear view mirror
The mirror used in astronomical telescope :
Concave
Convex
Spherical
Plano-convex lenses
A beam of light passes from air into a substance X.If the angle of incidence be 72° and the angle of refraction be 40°,calculate the refractive index of substance X .(Given :sin 72° = 0.951 and sin 40° = 0.642)
1.48
1.62
1.75
1.22
A converging lens has a focal length of 50 cm.The power of this lens is :
+0.2 D
-2.0 D
+2.0 D
-0.2 D