Obtain an expression for the frequency of a mass attached to a massless spring when it vibrates in a horizontal direction.

The frequency of the mass when it is displaced slightly is : .

Obtain an expression for the frequency of radiation emitted when a hydrogen atom de-excites form n to n-1 ,show that this frequency equals the classical frequency of revolution of the electron in the orbit.

Two blocks M_1 and M_2 having equal mass are free to move on a horizontal frictionless surface. M_2 is attached to a massless spring as shown in the figure. Initially M_2 is at rest and M_1 is moving towards M_2 with speed v and collides head-on with M_2

Obtain an expression for electric field intensity at any point on equitorial line of electric dipole. What is the direction of electric field?

Write an expression for the work done when a force is acting on an object in the direction of its displacment.