Question

Find out the false statement among the following. (1) The ejection of electrons when surface of a metal is irradiated by light is known as Compton effect. (2) Light, a well-known form of energy, is treated as a form of matter by saying that it consists of photons or bundles of energy. (3) Einstein's theory of photoclectric effect is based on Planck's quantum theory. (4) In photoclectric effect, the photocurrent does not depend on the frequency of photon but depends on the intensity of incident light.

Short answer

Statements (1) and (4) are false.

Step-by-step solution

Understand Statement (1)

Statement (1) refers to the ejection of electrons from a metal surface when it is irradiated by light, stating it is known as the Compton effect. This requires understanding the correct term for this phenomenon.

Analyze Statement (1)

The correct term for the phenomenon where electrons are ejected from a metal surface due to light irradiation is the photoelectric effect, not the Compton effect. The Compton effect involves scattering of X-rays and changes in wavelength.

Understand Statement (2)

Statement (2) explains that light is a form of energy treated as matter, consisting of photons or bundles of energy. This aligns with modern physics which describes light as quantized energy packets called photons.

Verify Statement (3)

Statement (3) asserts that Einstein's theory of the photoelectric effect is based on Planck's quantum theory. This is accurate because Einstein used Planck's idea of quantized energy to explain how light can eject electrons from a metal surface.

Verify Statement (4)

Statement (4) mentions that in the photoelectric effect, the photocurrent does not depend on the frequency of photons but depends on the light's intensity. This is false because the maximum kinetic energy of emitted electrons depends on the light frequency, whereas the photocurrent is influenced by light intensity.

Conclusion

Upon examining all statements, it is clear that statements (1) and (4) are false as per the explained reasoning.

Key concepts

Compton Effect

The Compton Effect describes the phenomenon where X-rays collide with electrons, leading to a change in wavelength, and thereby a shift in energy. This effect was discovered by Arthur H. Compton in 1923.
When X-rays hit an electron, the electron absorbs some of the photon's energy and is ejected from its atom. This results in a scattered photon that has less energy (longer wavelength) than the incoming one.
This demonstrated that light can behave not only as a wave but also as particles, or photons, supporting Einstein's photon theory of light. Remember, the Compton Effect is different from the photoelectric effect, which involves the ejection of electrons from a metal surface due to light irradiation.

Planck's Quantum Theory

Max Planck proposed the idea that energy is quantized, meaning it can only be emitted or absorbed in fixed amounts called 'quanta.' This theory marked a significant departure from classical physics.
Planck introduced the concept of energy quanta in 1900 when he was trying to explain blackbody radiation. He stated that the energy, E, of these quanta is proportional to the frequency, u, of the radiation: E = hν where h is Planck’s constant (6.62607015 x 10^−34 Js).
The introduction of this theory laid the foundation for quantum mechanics and opened new ways for understanding atomic and subatomic processes.
It also played an integral role in advancing further theories, such as Einstein's explanation of the photoelectric effect.

Einstein's Theory of the Photoelectric Effect

Albert Einstein extended Planck's quantum theory to explain the photoelectric effect in 1905, for which he later won the Nobel Prize in Physics.
In the photoelectric effect, electrons are ejected from the surface of a metal when it is irradiated with light. According to classic wave theory, increasing light intensity should increase the energy of ejected electrons. However, experiments showed that only the frequency of light matters.
Einstein proposed that light consists of photons with quantized energy. When a photon hits a metal, if it has enough energy (defined by its frequency), it can eject an electron. The equation for energy exchange in this effect is: E_photon = φ + KE where E_photon is the energy of the photon, φ is the work function of the metal (the minimum energy needed to eject an electron), and KE is the kinetic energy of the ejected electron.
This theory not only explained the experimental results but also helped solidify the quantum view of light and energy.