In which direction-towards or away from the lens, does he move the screen to focus the object?

An object is 2m away from a lens. Which forms an erect image 1/4th the size of the object, determine the focal length of the lens.What type of the lens is this?

When centripetal force acts on a body towards centre of the circle,why does the body not move towards the centre?

An iluminated object and a screen are placed 90 cm apart.Determine the focal length and nature of the lens required to produce a clear image on the screen,twice the size of the object.

A small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5.0 cm. (A) what is the separation between the objective lens and the eyepiece? (B) If this telescope is used to view a 100 m tall tower 3 km away, what is the height of the image of the tower formed by the objective lens?

A converging lens of focal length 6.25 cm is used as magnifying glass. If the near point of the observer is 25 cm from the eye and the lens is held close to the eye, calculate the distance of the object from the lens

A ocnverging bem of light forms of a sharp image on a screen. lens is placed in the path of the beam at 10 cm from the screen.It si found that screen has to be moved 8 cm further away from the lens to obtain a sharp image.Find the focal length and natrue of the lens.

Species diversity decreases as we move away from the equator towards the poles. What could be the possible reasons?