Question

Two mirrors each 1.6 m long are facing each other.
The distance between the mirrors is 20 cm. A light
ray is incident on one end of the mirror at an angle
of incidence of 30°. How many times is the ray
reflected before it reaches the other end?
​

Answer 1

Answer:

The distance between the mirrors is 20 cm. A light incident on one end of one of the mirrors at an angle of incidence of 30^(@). How many times is the ray reflected before it reaches the other end? therefore , actual number of reflection requried are 14

Answer 2

Answer:

Two mirrors each 1.6 m long are facing each other. The distance between the mirrors is 20 cm. A light ray is incident on one end of the mirror at an angle of incidence of 30°. How many times is the ray reflected before it reaches the other end?

​Explanation:

• In the above question:
• Given to us is- There are two mirrors each are of 1.6 m in length. They are facing each other. The distance between those two mirror is 20 cm. The angle of incidence of one f the mirror is 30 degree.
• We have to find how many times the ray will reflect before it reach to the other end of the mirror.
• We are not given what is the type of mirror, in such questions it is generally plain mirror.
• Therefore assuming it as plain mirror.
• As angle of incidence and angle of reflection is same for plain mirror, Therefore angle of reflection = 30 degree.
• There will be the diagram for this question, from the diagram-
• Calculating the distance- $tan A=\frac{d}{0.2}\\ tan30^{0}= \frac{d}{0.2}\\ d=\frac{0.2}{\sqrt{3} }$
• calculating total number of reflections=$N_{d} =\frac{1.6}{d}\\ \\= \frac{1.6}{\frac{0.2}{\sqrt{3} } } \\=13.85$
• Number of complete reflection is 13 + 1/6
• Here one is added as starting will be also counted. There fore 14 reflections.

Hence the total number of reflection will be 14.

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