Question

Given a block of glass that is semi-circular, a laser pointer, protractor/ruler, and index card, design your own experiment to observe and measure total internal reflection. Describe how you would shine the laser onto the glass block, what angles you would measure and how you would determine the critical angle from your measurements.

Answer 1

Answer:

Explanation:

Critical angle is angle of incidence at which the reflected ray is perpendicular to the normal of the plane.

Apply snell's law,

    ni sin∅i = nr sin ∅r

Here,ni & nr are reflective indices of incident and refracted media ,∅i is angle of incidence and ∅r is angle of refraction

In this case,the light refracted at interface of glass -air medium

ni=(1.52), nr =1.00(for air),∅r=90° and ∅i =∅c(from the definition of critical angle),

(1.52)sin∅c = (1.00)sin 90°

solve the equation for ∅c

∅c=sin⁻¹{(1.00)sin 90° /1.52}

=41.1°

thus,the critical angle is 41.1° .The rays which are incident greater than this angle,would reflect back into the same glass medium(total internal reelection)

Answer 2

Answer:

we go up the ramp there is a point where the beam is reflected inside the block, we carefully step back to the point where the beam is horizontal, we measure this angle which is our critical angle.

Explanation:

To design the experiment of measuring the critical angle, we describe the phenomenon, when the light passes from a medium with a higher refractive index to one with a lower index, it separates from the normal one and the Critical Angle is defined as the Angle for which the refraction occurs at 90º

            n₂ sin θ₂ = n₁ sin 90

           n₁ / n₂ = sin θ₂

As we can see, we have to measure the angle with which the laser touches the exit surface of the glass block.

Design of the experiment:

    We place the glass block on the ramp and at the top we hit the conveyor for half the angle, we climb the block on the ramp and see that the angle of incidence of lightning on the exit face changes, part of the beam comes out of the glass , we see it by dispersion in the particles of dirty in the air; Maybe the conveyor or the laser should be moved slightly so that the beam touches the point of origin on the conveyor.

   

   When we go up the ramp there is a point where the beam is reflected inside the block, we carefully step back to the point where the beam is horizontal, we measure this angle which is our critical angle.