Question:
The threshold wavelength for photoelectric emission from a material is \(5500Å\). Photoelectrons will be emitted, when this material is illuminated with monochromatic radiation from a
A. 75 W infra-red lamp
B. 10 W infra-red lamp
C. 75 W ultra-violet lamp
D. 10 W ultra-violet lamp
Choose the correct answer from the options given below:
The threshold wavelength for photoelectric emission from a material is \(5500Å\). Photoelectrons will be emitted, when this material is illuminated with monochromatic radiation from a
A. 75 W infra-red lamp
B. 10 W infra-red lamp
C. 75 W ultra-violet lamp
D. 10 W ultra-violet lamp
Choose the correct answer from the options given below:
A. 75 W infra-red lamp
B. 10 W infra-red lamp
C. 75 W ultra-violet lamp
D. 10 W ultra-violet lamp
Choose the correct answer from the options given below:
Show Hint
For photoelectric effect:
• Compare the radiation wavelength with the threshold wavelength.
• Only radiation with \(λ < λ_{threshold}\) causes emission.
Updated On: Mar 19, 2025
- A and D only
- C only
- C and D only
- B and C only
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The Correct Option is C
Approach Solution - 1
- Threshold Wavelength:
- Photoelectric emission occurs if \( \lambda < \lambda_{\text{threshold}} \).
- Given \( \lambda_{\text{threshold}} = 5500 \, \text{Å} \).
- Analysis of Radiation:
- Infra-red radiation has \( \lambda > 5500 \, \text{Å} \) (no emission).
- Ultra-violet radiation has \( \lambda < 5500 \, \text{Å} \) (emission occurs).
Options that are correct: C and D
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Approach Solution -2
Wavelength of infra-red = 700 nm (minimum)
Wavelength of UV = 100 – 400 nm
Since we need λ < 5000 Å
⇒ Only UV would be able to emit photoelectrons.
Wavelength of UV = 100 – 400 nm
Since we need λ < 5000 Å
⇒ Only UV would be able to emit photoelectrons.
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