A laser has `lambda= 7xx 10^(-7)`m and aperature `10^(-3)m` sends a beam to Moon which is at a distance of `4xx 10^(8)`m from the Earth. Deduce the angular spread of the beam and the areal spread as it reaches Moon.

Planet A is at a distance of 8.36xx10^(7) km from earth and planet B is 7.28xx10^(9) km from earth. Which planet is nearer to earth?

A ladder 10 m long reaches a window 8 m above the ground. Find the distance of the foot of the ladder from base of the wall.

A LASER is a source of very intense, monochromatic, and unidirectional beam of light. These properties of a laser light can be exploited to measure long distances. The distance of the Moon from the Earth has been already determined very precisely using a laser as a source of light. A laser light beamed at the Moon takes 2.56 s to return after reflection at the Moon’s surface. How much is the radius of the lunar orbit around the Earth ?

Two charges of +25 xx 10^-9 coulomb and -25 xx 10^-9 coulomb are placed 6 m apart. Find the electric field at a point 4 m from the centre of the electric dipole on axial line

A stress of 10^7 N m^-2 is required to break a material of density 4 xx 10^4 kg m^-3 . Calculate the length of a wire of this material, which can break under its own weight.