Physics 100% verified Theory questions

PHYSICS OBJ:

1-10) CCDBAACAAC

11-20) BCCCABBCBA

21-30)DDCDABCBAA

31-40)BDDBBCAABC

41-50)ABDABD**BA

a) A blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. ... A white body is one with a "rough surface [that] reflects all incident rays completely and uniformly in all directions."

Monochromatic color schemes are derived from a single base hue and extended using its shades, tones and tints. Tints are achieved by adding white and shades and tones are achieved by adding a darker color, grey or black. ... This is not monochromatic in the strictly scientific meaning of the word.

(of light or other radiation) of a single wavelength or frequency.

"it employs diffraction to focus monochromatic light"

b) In physics, two wave sources are perfectly coherent if they have a constant phase difference and the same frequency, and the same waveform. Coherence is an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference.

a fixed relationship between the phase of waves in a beam of radiation of a single frequency. Two beams of light are coherent when the phase difference between their waves is constant; they are noncoherent if there is a random or changing phase relationship.

c) A collimator is a device that narrows a beam of particles or waves. To narrow can mean either to cause the directions of motion to become more aligned in a specific direction (i.e., make collimated light or parallel rays), or to cause the spatial cross section of the beam to become smaller (beam limiting device).

Advantage of fiber optics

. Faster Speeds

Fiber optic cables have a core that carries light to transmit data. This allows fiber optic cables to carry signals at speeds that are only about 31 percent slower than the speed of light—faster than Cat5 or Cat6 copper cables. There is also less signal degradation with fiber cables.

3. Longer Distances

Fiber optic cables can carry signals much farther than the typical 328-foot limitation for copper cables. For example, some 10 Gbps singlemode fiber cables can carry signals almost 25 miles. The actual distance depends on the type of cable, the wavelength and the network.

4. Better Reliability

Fiber is immune to temperature changes, severe weather and moisture, all of which can hamper the connectivity of copper cable. Plus, fiber does not carry electric current, so it’s not bothered by electromagnetic interference (EMI) that can interrupt data transmission. It also does not present a fire hazard like old or worn copper cables can.

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Q7a) Doping is the process of adding impurities to intrinsic semiconductors to alter their properties. Normally Trivalent and Pentavalent elements are used to dope Silicon and Germanium. When an intrinsic semiconductor is doped with Trivalent impurity it becomes a P-Type semiconductor.

Forward Biased P-N Junction

When we connect p-type region of a junction with the positive terminal of a voltage source and n-type region with the negative terminal of the voltage source, then the junction is said to be forward biased. At this condition, due to the attraction of positive terminal of source, electrons which participated in covalent bond creations in p-type material, will be attracted towards the terminal. As result numbers of covalent bonds are broken and, electrons are shifted towards the positive terminal. As a result, the concentration of electrons in the crystal nearer to the terminal increases and these electrons recombine with holes here. In this way, the number of holes increases in the portion of the p-type region away from the junction, and it is reduced in the portion of p-type region nearer to the terminal. As such holes are shifted from terminal to junction.

Due to the higher concentration of holes adjacent to negative impurity ions layer the electrons of negative ions come out and recombine with those holes and create new holes in the layer. Consequently, the width of this negative ions layer is reduced and finally this layer vanishes.