If a and b are the width and height of rectangular wave-guide the cut off wavele

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Question
If a and b are the width and height of rectangular wave-guide the cut off wavelength ?_c for TE₂₀ mode is equal to
Options
A. a
B. a + b
C. a - b
D. a² + b²

Correct Answer

a

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1. In p mode of operation of magnetron the spikes due to phase focussing effect rotate at an angular velocity corresponding to
Options
A. one pole/cycle
B. two pole/cycle
C. four pole/cycle
D. six pole/cycle

2. Two identical hybrid tees are joined as shown in the given figure. If 16 mW power is fed into port 1, the power output at ports 2 , 3, 1', 2', 3' respectively is
Options
A. 8, 4, 2, 2, 0 mW
B. 0, 8, 4, 4, 0 mW
C. 0, 8, 2, 2, mW
D. 8, 2, 4, 2, 0 mW

3. A magic tee is to be used as CW duplexer. Then port 1, port 2, port 3 (E arm), port 4 (H arm) respectively should be connected to
Options
A. matched load, antenna, receiver and CW transmitter
B. CW transmitter, antenna, receiver and matched load
C. CW transmitter, receiver, antenna and matched load
D. CW transmitter, matched load, receiver and antenna

4. For a waveguide, which of the following statements is wrong?
Options
A. It is usually made of brass or aluminium
B. It is usually rectangular or circular in shape
C. The dielectric region is usually air
D. The wall thickness is very small as compared to skin depth

5. In a TWT the loss in attenuator is
Options
A. almost equal to forward gain of tube
B. much less than forward gain of tube
C. much higher than forward gain of tube
D. almost infinite

6. Assertion (A): In rectangular waveguide TE₀₁ mode is just TE₁₀ mode rotated by 90�.
Reason (R): When a rectangular waveguide is rotated by 90�, the broad and narrow dimensions get interchanged.
Options
A. Both A and R are correct and R is correct explanation of A
B. Both A and R are correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

7. In microwave system, waveguide twists
Options
A. change the plane of polarization of a propagating wave
B. change the direction of a propagating wave
C. change the mode of a propagating wave
D. both (b) and (c)

8. In TE₁₀mode the largest electric field in a rectangular wave guide, occurs
Options
A. along centre line of broad wall (i.e. x = a/2)
B. along the broad wall (i.e. x = 0 and x = a)
C. either (a) or (b)
D. neither (a) nor (b)

9. TM₀₁ mode in circular waveguide is analogous to
Options
A. TM₁₀ mode in square waveguide
B. TM₁₁ mode in square waveguide
C. TM₂₀ mode in square waveguide
D. TM₀₂ mode in square waveguide

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