Module 7 Quantum Model of Light

Question 1

What Is Black Body Radiation?

Answer 1

A black body is a theoretical object that perfectly absorbs and emits all radiation without reflecting any. Black Body Radiation is the electromagnetic radiation emitted by all objects with a temperature above absolute zero.

Question 2

What does Wien’s Law show?

Answer 2

Wien’s Law helps determine the peak wavelength of radiation emitted by a black body at a given temperature. The law states that the peak wavelength (λmax) is inversely proportional to the temperature (T) of the black body, and it can be expressed as λ_max = b / T

Question 3

Explain Plank’s contribution to the quantum model of light?

Answer 3

He proposed that electromagnetic radiation is emitted in discrete quantities or “packets” called quanta. This assumption led to the formulation of Planck’s Law, which accurately describes the black body radiation curve. Planck suggested that each quantum of energy (E) is proportional to the frequency (f) of the emitted radiation, given by:

E = hf

Question 4

Descibe The photoelectric effect

Answer 4

The photoelectric effect, first observed by Hertz, occurs when high-frequency light, such as ultraviolet light, shines on a metal surface, causing the emission of electrons. This emission only happens if the light’s frequency exceeds a certain threshold, regardless of its intensity. Once this frequency is reached, the number of emitted electrons increases with the light’s intensity, while their kinetic energy depends on the light’s frequency. The effect demonstrates that light’s energy is transferred to electrons, with excess energy converting to the electrons’ kinetic energy, supporting the particle theory of light.