one mark question
question 1
What is the distance between two convex lenses LA and LB with focal lengths FA and FB?
ans: FA+FB
question 2
If a medium has a critical angle for total internal reflection from the medium to vacuum as 300, what is the velocity of light in the medium?
ans: 1.5 × 108 m/s
question 3
What is the focal length of a double concave lens with a radius of curvature of 20 cm, if the refractive index of the glass with respect to the air is 5/3?
ans: -15 cm
question 4
The magnifying power of an astronomical telescope in normal adjustment is 100. What is the focal length of the objectives and eyepiece of the distance between them is 101 cm?
ans:100 cm and 1 cm respectively
question 5
If an equiconvex lens of focal length f and power P is cut into half in thickness, what is the focal length and power of each half?
ans:2f