
A student obtained a blurred image of an object on a screen by using a concave mirror. What should be done by him to obtain a sharp image on the screen?

Important Questions on Light - Reflection and Refraction

A student determines the focal length of a device , by focussing the image of a far off object on the screen positioned as shown in the figure below.
What is the device ?

A student determines the focal length of a device , by focussing the image of a far off object on the screen positioned as shown in the figure below.
What is the focal length of the device ?




Three students measured the focal length of a convex lens using parallel rays from a distant object. All of them measured the distance between lens and the inverted image of the screen. Student saw a sharp image on the screen and labelled the distance as .
Student saw a slightly larger blurred image on the screen and labelled the distance as .
Student saw a slightly smaller blurred image on the screen and labelled the distance as .
What relation most likely would be between the three measurements?

