Question

A student traces the path of a ray of light through a rectangular glass slab for the different values of angle of incidence namely 30 degree, 45 degree and 60 degree. He extends the direction of the incident ray by a dotted line and measures the perpendicular distance'l' between the extended incident ray and the emergent ray. Which observations are true?
a)'l' increases with increase in angle of incidence
b)'l' decreases with increase in angle of incidence
c)'l' remains the same even of the angle of incident changes
d)'l' is the maximum of angle of incidence 45 degree


Pls give the reason also:D

Answer 1

please mark as bran list

Answer 2

The perpendicular distance 'l' between the extended incident ray and emergent ray will increase with the increase in the angle of incidence.

• The perpendicular distance between the extended incident ray and emergent ray from a glass slab is called Lateral Displacement.
• Lateral Displacement is mathematically calculated as :

                         l = t($\frac{sin(i-r)}{cos r}$)

where  t is the thickness of the glass slab

            i is the angle of incidence

    and  r is the angle of refraction at the surface of the glass slab

From this formula we can draw the following conclusions:

1. Lateral displacement is directly proportional to the thickness of the glass slab.
2. As the angle of incidence increases, the term (i-r) also increases, hence sin(i-r) will also increase. So lateral displacement is directly proportional to the angle of incidence.

• In the given question, observations of lateral displacement are taken after increasing the angle of incidence, so l will also increase.

Therefore, option a) 'l' increases with the increase in the angle of incidence is correct.