A concave mirror of focal length ′f1′ is placed at a distance of ′d′ from a convex lens of focal length ′f2′. A beam of light coming from infinity and falling on this convex lens concave mirror combination returns to infinity. The distance ′d′ must equal to: (A) 2f1+f2 (B) −2f1+f2 (C) f1+f2 (D) −f1+f2

What type of questions asked from the lesson of magnetic effect of electric current 

Wavelength of green light is

A) 400-450 nm

B) 500-550 nm

C) 660-720 nm

D) 720-800 nm

What is the difference between anaerobic & aerobic respiration? Name some organism that uses the aerobic mode of respiration?

What are the main components of our environment? Explain each of them briefly.

What are examples of hydrotropism plants?