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Refraction of Light at Plane Surfaces — Question 8

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Question 8

A ray of green light enters a liquid from air, as shown in the figure. The angle 1 is 45° and angle 2 is 30°.

A ray of green light enters a liquid from air, as shown in the figure. The angle 1 is 45° and angle 2 is 30°. Find the refractive index of liquid. Show in the diagram the path of the ray after it strikes the mirror and re-enters in air. Mark in the diagram the angles wherever necessary. Redraw the diagram if plane mirror becomes normal to the refracted ray inside the liquid. State the principle used. Refraction of light at plane surfaces, Concise Physics Class 10 Solutions.

(a) Find the refractive index of liquid.

(b) Show in the diagram the path of the ray after it strikes the mirror and re-enters in air. Mark in the diagram the angles wherever necessary.

(c) Redraw the diagram if plane mirror becomes normal to the refracted ray inside the liquid. State the principle used.

Answer

(a) Refractive index of the liquid is given by Snell's law and is shown as below,

airμliquid = sin isin r\dfrac{\text{sin i}}{\text{sin r}}

airμliquid = sin 45°sin 30°\dfrac{\text{sin 45}\degree}{\text{sin 30}\degree}

=1212=22=2=1.414= \dfrac{\dfrac{1}{\sqrt{2}}}{\dfrac{1}{2}} \\[0.5em] = \dfrac{2}{\sqrt{2}} \\[0.5em] = \sqrt{2} \\[0.5em] = 1.414 \\[0.5em]

(b) Below labelled diagram shows the path of the ray after it strikes the mirror and re-enters in air:

A ray of green light enters a liquid from air, as shown in the figure. The angle 1 is 45° and angle 2 is 30°. Find the refractive index of liquid. Show in the diagram the path of the ray after it strikes the mirror and re-enters in air. Mark in the diagram the angles wherever necessary. Redraw the diagram if plane mirror becomes normal to the refracted ray inside the liquid. State the principle used. Refraction of light at plane surfaces, Concise Physics Class 10 Solutions.

(c) Below labelled diagram shows the path of the ray when it strikes the plane mirror normally inside the liquid:

A ray of green light enters a liquid from air, as shown in the figure. The angle 1 is 45° and angle 2 is 30°. Find the refractive index of liquid. Show in the diagram the path of the ray after it strikes the mirror and re-enters in air. Mark in the diagram the angles wherever necessary. Redraw the diagram if plane mirror becomes normal to the refracted ray inside the liquid. State the principle used. Refraction of light at plane surfaces, Concise Physics Class 10 Solutions.

The principle of reversibility is used.