This question has Statement-1 and Statement-2. Of the four choices given after the statements, choose the one that best describes the two statements.
Statement-1 : A metallic surface is irradiated by a monochromatic light of frequency v > v0 (the threshold frequency). The maximum kinetic energy and the stopping potential are Kmax and V0 respectively. If the frequency incident on the surface is doubled, both the Kmax and V0 are also doubled.
Statement -2 : The maximum kinetic energy and the stopping potential of photoelectrons emitted from a surface are linearly dependent on the frequency of incident light.
hv = hv0 + kmax
kmax = hv – hv0
This question involves the photoelectric effect, which describes how electrons are emitted from a material when light shines on it. Let's analyze both statements step by step.
The key equation for the photoelectric effect is Einstein's photoelectric equation:
where:
The stopping potential is the minimum voltage needed to stop the most energetic photoelectrons. It is related to by:
where is the charge of an electron. Combining these, we get:
or
Statement-1 claims: If the frequency is doubled (from to ), both and are doubled.
Let's test this with the equations. Initially:
After doubling the frequency:
Is ? Let's check:
But . These are equal only if , which is not true for any real material. Therefore, is not doubled when frequency is doubled. The same logic applies to stopping potential since it is directly proportional to . Thus, Statement-1 is false.
Statement-2 claims: and are linearly dependent on the frequency of incident light.
From the equations:
Both equations are of the form , where is or , is , is a constant ( or ), and is a constant ( or ). This is the definition of a linear relationship. Therefore, Statement-2 is true.
Since Statement-1 is false and Statement-2 is true, the correct choice is:
Statement-1 is false, Statement-2 is true.
Key Formulae:
Related Topics: The photoelectric effect is a fundamental phenomenon in quantum physics that demonstrates the particle nature of light (photons). It is crucial for understanding concepts like quantization of energy, wave-particle duality, and the interaction of light with matter.