Why does the bottom of a swimming pool always appear shallower than it actually is?
Why does the sun look slightly oval when it is near the horizon?
A stick partially dipped in water seems to be bent. Why?
Why do stars twinkle?
Is it possible to describe two situations of total internal reflection in a right-angled isosceles glass prism? Explain with diagram.
Why an object appears raised if placed at the bottom of a container filled with water?
Can total internal reflection be achieved if object originates in rarer medium? Explain with a diagram to justify you answer.
A ray of light in air strikes a glass surface. Is there a range of angles for which total internal reflection takes place?
Why does diamond sparkle?
Define critical angle and total internal reflection.
Why does a clear pool of water always appear to be shallower than it actually is?
Why do in summer, roads often appear to be covered with water when seen from a distance? Explain.
THEORETICAL QUESTIONS
Define lateral shift and derive an expression for it due to a parallel edged glass slab.
What causes the bending of light when it passes from one medium to another medium? Deduce the relation, [latex]\mu = \frac{Real\ depth}{Apparent\ depth}[/latex]
Define lateral shift. Derive an expression for it. Show in a graph the variation of lateral shift with the angle of incidence.
What do you mean by critical angles and total internal reflection? Derive a relation between critical angle and refractive index.
NUMERICAL PROBLEMS
A transparent cube of 12 cm edge contains a small air bubble. Its apparent depth when viewed through one face of the cube is 6 cm and when viewed through the opposite face is 2 cm. What is the actual distance of the bubble from the first face? Ans: 9 cm
Calculate the critical angle of (i) glass – water and (ii) water – air interfaces if object lies in the denser medium. Ans: 62.5o, 48.8o
An optical fiber with refractive index 1.72 is surrounded by a glass coating having refractive index 1.50. Find the critical angle for total internal reflection at the fiber glass interface. Ans: 60.7o
The critical angle for total internal reflection at a liquid air interface is 42.5o. If a ray of light travelling in the liquid has an angle of incidence at the interface of 35.0o, what angle does the refracted ray in the air make with the normal? Ans: 58.1o
Light from a luminous point on the lower face of a rectangular glass slab, 2 cm thick, strikes the upper face and the totally reflected rays outline a circle of 3.2 cm radius on the lower face. What is refractive index of the glass? Ans: 1.6
How long will the light take in travelling a distance of 500 m in water? Refractive index for water is 1.33 and velocity of light in vacuum is 3 x 108 m/s.Ans: 2.2 x 10-6 s
Light travelling through a pool of water in a parallel beam is incident on the horizontal surface. Its speed in water is 2.2 x 108 m/s. Calculate the maximum angle which the beam can make with the vertical of light to escape into the air where its speed is 3 x 108 m/s.Ans: 47.2o
