271. Transmission of power to a load over a transmission line achieves optimum value when standing-wave ratio (SWR) becomes—

1. 1. 2: 1

   
   
   

   2. 1: 2

   
   
   

   3. 1: 1

   
   
   

   4. 1: √2

   
   
   

---

1. View Hint View Answer Discuss in Forum

   Transmission of power to a load over a transmission line achieves optimum value when SWR becomes 1.

   Correct Option: C

   Transmission of power to a load over a transmission line achieves optimum value when SWR becomes 1.

---

272. When electromagnetic waves are reflected at an angle from a wall, their wavelength along the wall is—

1. 1. The same as in free space

   
   
   

   2. The same as the wavelength perpendicular to the wall

   
   
   

   3. Shortened because of the Doppler effect

   
   
   

   4. Greater than in the actual direction of propagation

   
   
   

---

1. View Hint View Answer Discuss in Forum

   The wavelength along the wall is greater than in the actual direction of propagation.

   Correct Option: D

   The wavelength along the wall is greater than in the actual direction of propagation.

---

---

273. Frequencies in UHF range propagate by means of—

1. 1. Ground wave

   
   
   

   2. Sky wave

   
   
   

   3. Space wave

   
   
   

   4. Surface wave

   
   
   

---

1. View Hint View Answer Discuss in Forum

   Frequencies in UHF range propagate by means of space waves.

   Correct Option: C

   Frequencies in UHF range propagate by means of space waves.

---

274. Match the different ionospheric layers with their virtual heights
     

     A. A D layer	1. 180 km
     B. E layer	2. 25-400 km
     C. F1 layer	3. 70 km
     D.F2 layer	4. 110 km

1. 1. A B C D
      1 3 2 4

   
   
   

   2. A B C D
      4 3 2 1

   
   
   

   3. A B C D
      3 1 4 2

   
   
   

   4. A B C D
      3 4 1 2

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

---

---

275. White noise is that signal whose frequency spectrum—

1. 1. Extends over infinite range

   
   
   

   2. Has flat spectral density

   
   
   

   3. Has spectral density varying as 1/f

   
   
   

   4. Has limited number of frequency components

   
   
   

---

1. View Hint View Answer Discuss in Forum

   White noise is a signal whose frequency spectrum has flat spectral density.

   Correct Option: B

   White noise is a signal whose frequency spectrum has flat spectral density.

---