The video explores the nature of light, initially understood as a wave, but later discoveries suggested it also behaves like a particle, leading to the concept of wave-particle duality. The ultraviolet catastrophe challenged classical physics, resolved by Planck's law, which introduced the idea of energy quanta. Einstein furthered this with the photoelectric effect, proving light's particle nature. The video concludes with the dual nature of light, foundational to quantum mechanics.

What was the initial understanding of light in the 19th century?

• Light is a particle.

• Light is a wave.

• Light is both a wave and a particle.

• Light is neither a wave nor a particle.

What problem did the Rayleigh-Jeans law encounter?

• It showed light only as a particle.

• It was unable to predict any experimental results.

• It predicted infinite power at high frequencies.

• It could not explain the photoelectric effect.

How did Planck's law resolve the ultraviolet catastrophe?

• By introducing the concept of continuous energy flow.

• By suggesting light is only a wave.

• By proving light is only a particle.

• By proposing energy exists in discrete packets called quanta.

What is the significance of Planck's constant in quantum mechanics?

• It is used to calculate the energy of a photon.

• It defines the wavelength of light.

• It represents the speed of light.

• It measures the intensity of light.

What did Einstein propose about light in relation to the photoelectric effect?

• Light energy travels in discrete packets called photons.

• Light energy travels in continuous waves.

• Light energy is unaffected by frequency.

• Light energy is only a theoretical concept.

According to particle theory, what is required for an electron to be ejected from a metal?

• A photon with no energy.

• A photon with energy greater than the work function.

• A photon with energy equal to the work function.

• A photon with energy less than the work function.

What does the wave-particle duality of light imply?

• Light behaves only as a wave.

• Light behaves only as a particle.

• Light can behave as both a wave and a particle depending on the situation.

• Light does not exist in any form.