Physics Essay Example

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20 February 2021

Section B

Question 1

Antennas are oriented in a particular plane to best receive the signal from the transmitting plane that emits a radio wave since in such orientation, it ensures that both the receiving and transmission antennas have a maximum directive gain of each other [ CITATION RDe03 l 2057 ].

Question 2

Laser Airborne Depth Sounder (LADS) is a device used to measure accurately the depth of both sea and fresh water. Basically, LADS functions by measuring the time difference that occurs on emission and reception of wave pulses which are reflected from the bottom of the water body as well as water surface [ CITATION Pat12 l 2057 ]. Since the speed of the emitted wave is known, the depth is calculated using the formula below


The procedure of measuring the depth of the sea water is as described below

  1. A plane directs a beam of laser (from an infra-red laser) light onto the water body

  2. The emitted light is then reflected from the water body onto the plane.

  3. To produce a beam of green visible light, an electronic device attached to the plane doubles the frequency of the laser light.

  4. Infrared light is reflected from the surface of the water body, green light passes through the sea surface and is reflected by the sea bottom. This is as shown in fig. 1 below

Physics 1Physics 2Physics 3Physics 4Physics 5


Physics 6

Fig. 1. Measuring of depth of a sea.

The time delay that occurs between a pulse of the infrared and green light being measured in combination with equation 1 above are used to determine the sea depth.

Question 3

  1. Light source must be coherent for the waves to superimpose.

  2. The intensity of light at P is very high i.e. the point is very Bright. This is because at the point, constructive interference occurs resulting into superposition of the two light waves.

  3. Physics 7assuming it’s a first order,
    Physics 8=
    Physics 9

  1. The wavelength of the light used was calculated as below

Physics 10

Physics 11

The wavelength used is
Physics 12

Question 4

Slit Spacing = 1/7000=1.429*10-4 cm

Physics 13

The wavelength is
Physics 14

Question 5

Physics 15

Physics 16 thus in this case
Physics 17

Physics 18

Thus the maximum number of orders possible is 1

Question 6

The construction of a compact disk is such that it consists of sets of irregularities known as pits and lands. The occurrence of this pits and lands is in a sequence that corresponds to the data that is on the compact disk. A compact Disk player is composed of a laser that has the ability to scan over the track of the compact disk and read the pits and lands. The scanner reads this by detecting phase difference that occurs between the reflected beams. Using the phase difference, the scanner is able to distinguish between pits and lands, and as a result, Binary data is generated.

Question 7

  1. The incident light source on striking the photoelectric cell, electrons are emitted. Since the electrons have sufficient energy and the variable voltage supply is set to zero, they overcome the resistance and flow through the circuit. The variable resistor is then adjusted such that enough current is produced that counteract the flow of the electrons. This is done until there is no current flowing through the current, i.e. the ammeter reading is zero. At this point when there is no current flow, the value of the variable voltage supply is the stopping potential. Given by the equation;

Physics 19

Thus a plot of stopping voltage against frequency shows relationship.

  1. Light of enough frequency on striking a metal surface, there is production of electrons.

Flow of electrons results into production of current.

  1. Light waves is composed of photons. This photons have energy. When the photons with sufficient energy strikes a metal surface, energy is transferred from the photons to the electrons on the metal surface. The electrons on gaining sufficient energy, are ejected from the surface and, since they are negatively charged, are attracted towards a positively charged electrons. As they move, current flow is generated.

Question 8

Energy of the photon is given by
Physics 20

  1. In this case, the plank’s Constant is 6.626 × 10-34 Js, Speed of the light is 3 × 108 m/s and wavelength of the photon is 600 Nano meters

Thus the photon Energy is;

Physics 21

  1. The kinetic Energy of the most energetic photon

Physics 22

Thus the kinetic Energy of the most energetic photon is 0.372eV

  1. The stopping Voltage

Stopping Voltage is give as

Physics 23

Question 9

Converting 30keV to joules

Physics 24

From the equation
Physics 25 it implies that
Physics 26

Physics 27

Thus the frequency is
Physics 28

Question 10

Physics 29

Physics 30

  1. Physics 31This Implies that
    Physics 32

Physics 33

  1. Electron Microscope utilizes beam of electrons that in magnifying objects and this gives it a high resolution unlike light microscope.


Carbonneau, Patrice. Fluvial Remote Sensing for Science and Management. John Wiley & Sons, 2012.

Straw, R. Dean. The ARRL antenna book: The Ultimate Reference for Amateur Radio Antennas. ARRL, 2003.