A young man has to hold a book at arm's length to be able to read it clearly.The defect of vision is :

Linear magnification produced by a concave mirror may be :

The refraction of light is commonly known as

Myopia can be corrected by using

Which type mirror is used in box-type solar cooker?

If R is the radius of curvature of a spherical mirror and f is its focal length,then :

A person cannot see the distant objects clearly (though he can see the near by objects clearly).He is suffering from the defect of vision called :

SI unit of power is

A concave mirror cannot be used as :

The sum of the reciprocals of object distance and image distance is equal to the