Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NEETPhysicsDual Nature of Matter

A beam of monochromatic light of wavelength 500 nm and power 6 W falls normally on a perfectly reflecting plane mirror. The force exerted by the light beam on the mirror is: (c = 3 10^8 m/s )

Options

  1. A2 10⁻⁸ N
  2. B1.8 10⁹ N
  3. C4 10⁻⁸ N
  4. D1 10⁻⁸ N

Correct answer

C. 4 10⁻⁸ N

Step-by-step solution

The force exerted by a light beam on a surface is equal to the rate of change of momentum of the photons. For a perfectly reflecting surface, the change in momentum for each photon is p = 2h . If n photons strike the surface per second, the total force is: F = n p = n ( 2h ) The power of the beam is P = n ( hc ) . From this, we can express the force directly in terms of power: F = 2P c Notice that the wavelength of the light is not required to find the force when the power is known. Substitute the given values: F =

Practice Dual Nature of Matter on Quantrex Academy →

More from Dual Nature of Matter

An electron and positron are accelerated from rest to the same kinetic energy. The ratio of their de Broglie wavelengths is 2026An electron of mass m and charge e initially at rest gets accelerated by a constant electric field E. The de-Broglie wavelength of the electron at time t is (h = Planck's constant) 2026The wavelength _e of an electron and _P of a photon of same energy E are related as 2026A light of wavelength ( < ₀) falls on a metal surface. The momentum of the fastest moving electron is p . In order to have the momentum of an electron equal to 2p , the required wa 2026The de Broglie wavelength of an electron with kinetic energy K₁ is ₁ . If the kinetic energy increases to 5K₁ , the new wavelength is ₂ = x ₁ . The value of x is 2026A student plots two different graphs using the same photoelectric experiment data. 1. Maximum kinetic energy ( K_ max ) against frequency ( ) 2. Stopping potential ( V_o ) against 2026In a photoelectric cell, for the incident radiation of wavelength , the fastest electron has speed 'v'. If the wavelength of incident radiation is changed to 3 , the speed of the f 2026A particle is dropped from a height ' y '. The de-Broglie wavelength of the particle as a function of height is 2026 Full Dual Nature of Matter list All NEET PYQs