A laser beam enters a 16.5 cm thick glass window at an angle of 58.0° from the normal. The index of refraction of the glass is 1.47. At what angle from the normal does the beam travel through the glass?

= 35.23°

time taken = 0.9898 ns

Explanation:

Using Snell's law as:

Where,  

 is the angle of incidence  ( 58.0° )

is the angle of refraction  ( ? )

is the refractive index of the refraction medium  (glass, n=1.47)

is the refractive index of the incidence medium (air, n=1)

Hence,

Angle of refraction= sin⁻¹ 0.5769 = 35.23°

The distance it has to travel

d =  = 16.5 cm / cos 35.23° = 20.20cm

Also,

n = c/v.

Speed of light in vacuum = 3×10¹⁰ cm/s

Speed in the medium is:

v = c/n = 3×10¹⁰ cm/s / 1.47

  = 2.0408 × 10¹⁰ cm/s

The time taken is:

t = d/s

  = 20.20 cm / 2.0408×10¹⁰ cm/s

  = 9.898 × 10⁻¹⁰ s

   = 0.9898 × 10⁻⁹ s

Also,

1 ns = 10⁻⁹ s

So, time taken = 0.9898 ns

weight of the box is given as

here this is placed on the inclined of angle 42 degree

now this weight will have two components one is along the incline other is perpendicular to it

so here we need to apply a force parallel to incline opposite to its component of weight

so here the component of weight is given as

here we have

so it requires 75 n force to move it upwards