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For energy density, power and intensity ...

For energy density, power and intensity of any wave choose the correct options.

A

`u = "energy density" = (1)/(2)rhoomega^(2)A^(2)`

B

`P = "power" = (1)/(2)rhoomega^(2)A^(2)Sv`

C

`I = "intensity"= (1)/(2)rhoomega^(2)A^(2)Sv`

D

`I = (P)/(S)`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question regarding the energy density, power, and intensity of any wave, we will analyze each option step by step. ### Step 1: Analyze Energy Density The first option states that energy density \( U \) is given by: \[ U = \frac{1}{2} \rho \omega^2 A^2 \] Where: - \( \rho \) is the density of the medium, - \( \omega \) is the angular frequency, - \( A \) is the amplitude of the wave. This formula is indeed correct. Energy density represents the amount of energy stored in a unit volume of the wave. **Conclusion for Step 1**: Option A is correct. ### Step 2: Analyze Power The second option states that power \( P \) is given by: \[ P = \frac{1}{2} \rho \omega^2 A^2 S V \] Where: - \( S \) is the cross-sectional area, - \( V \) is the wave velocity. Power can be calculated as the energy transferred per unit time. The energy transferred can be expressed as energy density multiplied by volume, and the volume can be represented as the cross-sectional area multiplied by distance traveled per unit time (which is the wave velocity). Using the energy density from Step 1, we can express power as: \[ P = U \cdot \text{Volume} = U \cdot (S \cdot V) = \left(\frac{1}{2} \rho \omega^2 A^2\right) (S \cdot V) \] Thus, this option is also correct. **Conclusion for Step 2**: Option B is correct. ### Step 3: Analyze Intensity The third option states that intensity \( I \) is given by: \[ I = \frac{1}{2} \rho \omega^2 A^2 S V \] However, intensity is defined as power per unit area: \[ I = \frac{P}{A} \] Rewriting this using the expression for power from Step 2: \[ I = \frac{\frac{1}{2} \rho \omega^2 A^2 S V}{S} = \frac{1}{2} \rho \omega^2 A^2 V \] This shows that the expression given in option C is incorrect because it does not account for the correct relationship between intensity and power. **Conclusion for Step 3**: Option C is incorrect. ### Step 4: Verify Intensity Again The fourth option states: \[ I = \frac{P}{S} \] This is indeed the correct definition of intensity, as it states that intensity is power per unit area. Since we have already established that power can be expressed in terms of energy density and area, this option is correct. **Conclusion for Step 4**: Option D is correct. ### Final Summary of Options - Option A: Correct - Option B: Correct - Option C: Incorrect - Option D: Correct
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