This set of Radar Multiple Choice Questions & Answers (MCQs) focuses on “Types of Simple Targets”.
1. Instead of the radar wavelength, the radar cross section upon the characteristics of the object.
a) True
b) False
View Answer
Explanation: It is true that the radar cross section depends on the characteristic dimensions of the object compared to the radar wavelength because when the wavelength is large compared to the object’s dimensions, scattering is said to be in the Rayleigh region.
2. In which out of the following conditions wavelength is smaller compared to the object’s dimensions?
a) Resonance region
b) Thermal region
c) Rayleigh region
d) Optical region
View Answer
Explanation: In Optical region the wavelength is smaller compared to the object’s dimensions. Scattering from aircraft or ships at microwave frequencies generally in the optical region. Here, instead of getting affected from its projected area, the radar cross sections is affected more by the shape of the object.
3. Which out of the following is not an example of a simple target?
a) Cone
b) Cylinder
c) Ogive
d) Missile
View Answer
Explanation: Cone, cylinder, ogive are examples of simple targets however missile is a complex target. Simple targets have simpler cross sections and the total cross section of a simple target is obtained by summing vectorially the contributions from the individual simple shaped.
4. In the resonance region of sphere, 2πa/λ ≫ 1, the physical area of the sphere with the frequency is increased as approached by the radar cross section.
a) True
b) False
View Answer
Explanation: It’s the optical region where the radar cross section approached the physical area of the sphere as the frequency is increased since here scattering does not take place over the entire hemisphere that faces the radar, but only from a small bright spot at the tip of the smooth sphere.
5. What happens when the viewing angle is decreased in a long thin wire or rod?
a) Backscatter becomes steadier
b) Creeping wave travels around the sphere
c) Backscatter levels off and increases
d) Greater loss and smaller magnitude
View Answer
Explanation: When the viewing angle decreases, an angle is reached where the backscatter levels off and then increases. This is because of the surface traveling wave which cannot be predicted from classical physical optics scattering theory.
6. In which of the following case, surface traveling cannot occur?
a) Sphere
b) Flat plate
c) Wing of an aircraft
d) Ogive
View Answer
Explanation: Surface traveling cannot occur in sphere. The traveling wave is launched when the incident electric field has components perpendicular and parallel to the surface and lies in the plane of incidence defined by direction of incidence and the surface normal.
7. If the travelling wave portion of a long thin wire is made up of resistive material, the echo ___________
a) forms an ellipse
b) reduces
c) increases
d) disappears
View Answer
Explanation: The travelling wave portion of the echo is reduced if the surface is made of resistive material because of which attenuation occurs as the wave travels down the surface and back, not to mention according to Knott, the traveling mechanism has an effect near broadside incidence.
8. In flat plate, the polarization of a radar wave is defined by __________
a) the orientation of the electric field
b) the orientation of electric as well as a magnetic field
c) the orientation of the magnetic field
d) the orientation of the transmission axis
View Answer
Explanation: The polarization of a radar wave is defined by the orientation of the electric field. This is just like when the electric field is in the vertical direction, vertical polarization occurs. The scattering behavior is not simple for a flat plate even though it’s a simple target, that’s why it has both vertical and horizontal polarization.
9. When do we obtain a larger value of cross section when a radar views a cone?
a) Viewed perpendicular to its surface
b) Viewed from the bottom
c) Viewed parallel to its surface
d) Viewed from top
View Answer
Explanation: A large value of cross section occurs when the radar views the cone perpendicular to its surface. It is true that the radar cross section does not depend significantly on the cone angle or the volume. Not to mention from the rear, the cross section is that of a sphere.
10. In a cone-sphere, echoes from the tip and the join between the cone and the sphere, as well as from ____________
a) wavelength of target
b) vertical polarization
c) backscatter field
d) creeping wave
View Answer
Explanation: The echoes also comes from a creeping wave that travels around the sphere. The first derivatives of the cone and the sphere at the join are usually equal, but the curvature is not continuous because there is no backscatter when viewed from the sides.
Sanfoundry Global Education & Learning Series – Radar.
To practice all areas of Radar, here is complete set of Multiple Choice Questions and Answers.
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