The Question is from neet-physics dual-nature-matter-radiation , and it was created by the author ABDUL JILANI BASHA

Question

In Lenard's photoelectric experiment, which observation definitively proves the particle nature of light?

ABDUL JILANI BASHA · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Photoelectric Effect and Particle Nature of Light
 **Related Topics**: Quantum mechanics, wave-particle duality, Planck's constant
 **Prerequisites**: Understanding of light as an electromagnetic wave and the concept of energy quanta (photons).
## SOLUTION PATHWAY
**Given Information**:
  Lenard's photoelectric experiment observations.
  Options describing different observations.
**Method & Steps**:
 1. Analyze each option to determine which observation directly supports the particle nature of light.
  Reasoning: The photoelectric effect demonstrates that light interacts with matter as discrete packets of energy (photons), not as a continuous wave.
  Formula/Rule:  $E = hf$, where $E$ is the energy of a photon, $h$ is Planck's constant, and $f$ is the frequency of light.
 2. Evaluate each option in the context of the energy-frequency relationship of photons.
  Working: 
        * Option A: Increasing intensity increases the *number* of photons, but not the energy of individual photons. This doesn't directly prove the particle nature.
        * Option B: Same as A; more photons, but not a change in individual photon energy.
        * Option C: The existence of a threshold frequency ($f_0$) means that a minimum energy ($hf_0$) is required to eject a photoelectron. This directly supports the idea that light energy comes in discrete packets (photons). Below this threshold frequency, even with high intensity (many photons), no electrons are emitted because individual photons lack sufficient energy.
        * Option D: While true, this observation doesn't directly demonstrate the quantized nature of light.
 3. Conclude which option best demonstrates the particle nature of light.
  Result: Option C, the existence of a threshold frequency, is the observation that definitively proves the particle nature of light. This is because it shows that the energy of light is not continuous but comes in discrete packets (photons), each with energy proportional to its frequency.
  Verification: The threshold frequency directly relates to the minimum energy required to overcome the work function of the metal, demonstrating the quantized nature of light's energy.
 ## OPTION ANALYSIS
A :x: Increasing intensity increases the number of photons, not the energy of individual photons. This doesn't directly demonstrate the particle nature of light.
B :x: Similar to A; more photons, but not a change in individual photon energy.
C ✓: The threshold frequency demonstrates the quantized nature of light energy. Below the threshold, no photoelectrons are emitted, regardless of intensity, because individual photons lack sufficient energy to overcome the work function of the metal.
D :x: While true, this observation does not directly demonstrate the quantized nature of light.  It is a consequence of the particle nature, but not definitive proof.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing intensity with energy: Intensity relates to the number of photons, not the energy of each photon.
  How to avoid: Remember that $E=hf$ relates energy to frequency, not intensity.
  2.Misinterpreting stopping potential: Stopping potential is related to the maximum kinetic energy of emitted electrons, but doesn't directly show quantization.
  How to avoid: Focus on the existence of a threshold frequency as the key indicator of the particle nature of light.
 **Quick Tips**:
  1.Remember the equation $E = hf$ and how it relates to the threshold frequency.
  2.Focus on the fact that below the threshold frequency, no electrons are emitted regardless of intensity, which is a direct consequence of the particle nature of light.

ABDUL JILANI BASHA · Answer

The kinetic energy of photoelectrons increases with increasing light intensity.

ABDUL JILANI BASHA · Answer

The number of photoelectrons emitted increases with increasing light intensity.

ABDUL JILANI BASHA · Answer

The correct Option is "Existence of a threshold frequency below which no photoelectrons are emitted, regardless of intensity"

ABDUL JILANI BASHA · Answer

The stopping potential is independent of the intensity of light.

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