Numerical Problem on Light Reflection and Refraction
Q1: How fast does the light travel in a glass of refractive index 1.5?
Answer:
By Snell's law, refractive index (n) is the ratio of i.e.
Q2:When a bright object is placed 10 cm away from a concave mirror, its real image is formed at a distance 40cm from the mirror. What is the focal length of the mirror?
Answer:
Q3: If the angle of incidence of a ray of light falling on the glass surface is 30° and the angle of refraction is 19°. what is the refractive index of glass?
Ans:
angle of incidence i = 30°
angle of refraction r = 19°
refractive index n = sin i/sin r = sin 30/sin 19
n = .5/.3256 = 1.535 ....(ans)
Q4: If a child crawls towards a mirror at a rate of 0.20 m/s, then at what speed will the child and her image come nearby to each other?
Ans: In 1 sec, the child moves towards the mirror by a distance of 0.20 meters. In the same second, her image also moves 0.20m closer.
Therefore, the child and her image comes closer to each other by 0.40m per second.