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A plane electromagnetic wave is incident...

A plane electromagnetic wave is incident on a material surface. The wave delivers momentum p and energy E.

A

`p = 0, E!= 0.`

B

`p!=0, E=0.`

C

`p!=0, E!=0.`

D

`p=0, E=0.`

Text Solution

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The correct Answer is:
To solve the problem, we need to analyze the relationship between the momentum \( P \) and energy \( E \) of a plane electromagnetic wave incident on a material surface. ### Step-by-Step Solution: 1. **Understanding the Definitions**: - The energy \( E \) of a photon (quantum of electromagnetic wave) is given by the equation: \[ E = h \nu \] where \( h \) is Planck's constant and \( \nu \) is the frequency of the wave. - The momentum \( P \) of a photon can be expressed as: \[ P = \frac{E}{c} \] where \( c \) is the speed of light. 2. **Relating Energy and Momentum**: - From the above equations, we can express momentum in terms of frequency: \[ P = \frac{h \nu}{c} \] - This shows that if the frequency \( \nu \) is non-zero, then \( P \) must also be non-zero. 3. **Analyzing the Options**: - **Option 1**: \( P = 0, E \neq 0 \) - This is not possible because if \( E \) is non-zero, then \( P \) must also be non-zero. - **Option 2**: \( P \neq 0, E = 0 \) - This is also not possible because if \( P \) is non-zero, then \( E \) cannot be zero. - **Option 3**: \( P \neq 0, E \neq 0 \) - This is possible and consistent with our analysis. - **Option 4**: \( P = 0, E = 0 \) - This is not possible in the context of an incident electromagnetic wave, as it would imply no energy or momentum is delivered. 4. **Conclusion**: - The only valid option is **Option 3**: \( P \neq 0 \) and \( E \neq 0 \). This means that when an electromagnetic wave strikes a surface, it delivers both momentum and energy.
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