Test: Planck’s Quantum Theory - JEE MCQ

We have E = hc/λ
E₁/E₂ = 4000Å/2000Å = 2

The speed of light (electromagnetic radiation) through vacuum has a constant value of 3.00 x 10⁸m/s and is independent of the wavelength in vacuum.

The wavelength (λ) and frequency (ν) of electromagnetic wave is related by the equation c = λ.ν,

Where c is the speed of light = 3.00 x 108 m/s, λ is the wavelength in m and ν is the frequency is s^-1or Hz.

Substituting the values in the formula, we get,

c = λ.ν

ν = c/λ

ν = 3.0 x 10⁸ / 3.12 x 10^-5

= 0.96 x 10¹³ m =  9.62 X 10¹²

If light beyond a specific threshold frequency hits a metal surface, electrons are ejected from the surface of the metal. The minimum energy required to eject an electron from the surface is called the work function of the metal. These ejected electrons are called photoelectrons. The kinetic energy of the most energetic electron among these photoelectrons is called the maximum kinetic energy.

The total possible values of m for l range from – through 0 to +. 

 = 1.51 × 10^-17 J.

Wavenumber is defined as the number of complete wave cycles per unit length of a linear space. It can also be referred to as the spatial frequency of the waves represented in radians per unit distance, or cycles per unit distance. It is usually measured in units of reciprocal centimeters (cm^-1) and reciprocal meters (m^-1).

The speed of all form of electromagnetic wave is related by the equation c = λ.v, whereby, λ = 3.0 x 10⁸ / 1.2 x 10¹³ = 2.5 x 10 ^-5 m.

Radio waves, infrared rays, visible light, ultraviolet rays, X-rays, and gamma raysare all types of electromagnetic radiation. Radio waves have the longest wavelength, and gamma rays have the shortest wavelength.

Max Planck gave the Planck’s quantum theory and was the first to determine the value of h which is the Planck’s constant.

As E=h(frequency) E is directly proportional to frequency and as frequency = speed of light / wavelength frequency is inversely proportional to wavelength.

The wavelength (λ) and frequency (ν) of electromagnetic wave is related by the equation c = λ.ν, whereby, λ = 3.0 x10⁸ / 4.62 ×10¹⁴ =  0.649 x 10^-6 m = 649nm