Question
An observer can see through a pin–hole the top end of a thin rod of height h, placed as shown in the figure. The beaker height is 3h and its radius h. When the beaker is filled with a liquid up to a height 2h, he can see the lower end of the rod. Then the refractive index of the liquid is
- 5/2
- 3/2
The correct answer is:
The line of sight of the observer remains constant, making an angle of 45° with the normal.
=
Related Questions to study
A diverging beam of light from a point source S having divergence angle a, falls symmetrically on a glass slab as shown. The angles of incidence of the two extreme rays are equal. If the thickness of the glass slab is t and the refractive index n, then the divergence angle of the emergent beam is
A diverging beam of light from a point source S having divergence angle a, falls symmetrically on a glass slab as shown. The angles of incidence of the two extreme rays are equal. If the thickness of the glass slab is t and the refractive index n, then the divergence angle of the emergent beam is
A rectangular glass slab ABCD, of refractive index n1, is immersed in water of refractive index 
A ray of light in incident at the surface AB of the slab as shown. The maximum value of the angle of incidence amax, such that the ray comes out only from the other surface CD is given by
A rectangular glass slab ABCD, of refractive index n1, is immersed in water of refractive index A ray of light in incident at the surface AB of the slab as shown. The maximum value of the angle of incidence amax, such that the ray comes out only from the other surface CD is given by
A smooth block is released at rest on a incline and then slides a distance d. The time taken to slide is n times as much to slide on rough incline than on a smooth incline. The coefficient of friction is-
A smooth block is released at rest on a incline and then slides a distance d. The time taken to slide is n times as much to slide on rough incline than on a smooth incline. The coefficient of friction is-
A block is kept on a friction less inclined surface with angle of inclination . The incline is given an acceleration a to keep the block stationary. Then a is equal to-
A block is kept on a friction less inclined surface with angle of inclination . The incline is given an acceleration a to keep the block stationary. Then a is equal to-
If the sides a, b, c of a triangle are in G.P. and largest angle exceeds the smallest by 
, then 
If the sides a, b, c of a triangle are in G.P. and largest angle exceeds the smallest by , then
Two plane mirrors. A and B are aligned parallel to each other, as shown in the figure. A light ray is incident at an angle of 
at a point just inside one end of A. The plane of incidence coincides with the plane of the figure. The maximum number of times the ray undergoes reflections (including the first one) before it emerges out is
Two plane mirrors. A and B are aligned parallel to each other, as shown in the figure. A light ray is incident at an angle of at a point just inside one end of A. The plane of incidence coincides with the plane of the figure. The maximum number of times the ray undergoes reflections (including the first one) before it emerges out is
A point source of light B is placed at a distance L in front of the centre of a mirror of width d hung vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror at a distance 2L from it as shown. The greatest distance over which he can see the image of the light source in the mirror is
A point source of light B is placed at a distance L in front of the centre of a mirror of width d hung vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror at a distance 2L from it as shown. The greatest distance over which he can see the image of the light source in the mirror is
Figure shows a glowing mercury tube. The illuminances at point A, B and C are related as
Figure shows a glowing mercury tube. The illuminances at point A, B and C are related as
A block rests on a rough inclined plane making an angle 
of with the horizontal. The coefficient of static friction between the block and the plane is 0.8. If the frictional force on the block is 10 N, the mass of the block (in kg) is : 
A block rests on a rough inclined plane making an angle of with the horizontal. The coefficient of static friction between the block and the plane is 0.8. If the frictional force on the block is 10 N, the mass of the block (in kg) is :
In 
then the triangle is.
In then the triangle is.
Two masses 
tied to a string are hanging over a light friction less pulley. What is the acceleration of the masses when they are free to move ? (g=9.8
)
Two masses tied to a string are hanging over a light friction less pulley. What is the acceleration of the masses when they are free to move ? (g=9.8)
A machine gun fires a bullet of mass 40 g with a velocity 1200 
. The man holding it, can exert maximum force of 144 N on the gun. How many bullets can he fire per second at the most?
A machine gun fires a bullet of mass 40 g with a velocity 1200 . The man holding it, can exert maximum force of 144 N on the gun. How many bullets can he fire per second at the most?
One end of massless rope, which passes over a massless and frictionless pulley P is tied to a hook C while the other end is free. Maximum tension that the rope can bear is 840 N. With what value of maximum safe acceleration (in 
) can a man of 60 kg climb on the rope
One end of massless rope, which passes over a massless and frictionless pulley P is tied to a hook C while the other end is free. Maximum tension that the rope can bear is 840 N. With what value of maximum safe acceleration (in ) can a man of 60 kg climb on the rope
Three identical blocks of masses m = 2 kg are drawn by a force F with an acceleration of 0.6 ms–2 on a frictionless surface, then what is the tension (in N) in the string between the blocks B and C
Three identical blocks of masses m = 2 kg are drawn by a force F with an acceleration of 0.6 ms–2 on a frictionless surface, then what is the tension (in N) in the string between the blocks B and C
When forces 
are acting on a particle of mass m such that and are mutually perpendicular, then the particle remains stationary. If the force is now removed then the acceleration of the particle is-
When forces are acting on a particle of mass m such that and are mutually perpendicular, then the particle remains stationary. If the force is now removed then the acceleration of the particle is-
