1) The document is an optics lab assignment submitted by Fareena Shahid containing short questions and multiple choice questions about Fresnel's biprism experiment and the ionization potential of mercury experiment. 2) The Fresnel's biprism experiment apparatus includes lenses, lens mounts, an optical bench, a He-Ne laser, and a measuring tape. One precaution is to handle the optical equipment carefully. The experiment involves observing the interference pattern and measuring the virtual source separation. 3) The multiple choice questions ask about the number of prisms in Fresnel's experiment, the measuring tape length, the light source used, and how the virtual sources are obtained. 4) The

1. NAME;
FAREENA SHAHID
SUBJECT;
OPTICS LAB IV
ASSIGHNMENT;
SHORT QUESTIONS AND MCQ’S
SUBMITED TO;
DANISH ABID

2. SHORT QUESTIONS;
1. Fresnel’s Biprism
1) What is mean by Fresnel’s biprism?
Answer; A Fresnel Biprismis a variation on the Young's Slits experiment. The
Fresnelbiprismconsists of two thin prisms jointat their bases to forman isosceles
triangle.
2) Draw a diagram of Fresnel’s biprism?
Answer;
3) What is the apparatusof Fresnel’s biprism?
Answer ;
• Lenses (f = 20 mm and 300 mm).
• Lens mounts.
• Swinging arm and slide mounts.
• Optical bench.
• Laser, He-Ne 1.0 mW, 220 V AC.
• Measuring tape, 200 cm.

3. 4) Write down one precautionof Fresnel’s ?
Answer ; . Optical systems aresensitiveand are often fine-tuned. Be very careful
with the equipment, as a slight nudge might damage the equipment.
5) Write down steps of experiment?
Answer; there are two steps of experiment,
i. Interferencepattern
ii. Virtual sourceseparation
MCQ’S
1) How many prism is used in fresnels?
a) One
b) Two
c) Three
2) What is the length of measuring tape in apparatus?
a) 100mm
b) 200cm
c) 350mm
3) Which light source use,
a) Ar laser
b) Kr laser
c) He-Ne laser
4) . Calculate the distance g between the virtual sources and the lens
H (object distance) using the imaging equation:
a) 𝑑𝑛 = 𝐷𝑛/5
b) 𝒈 =
𝒇𝒃
𝒃−𝒇
5) In the Fresnel’s Biprism experiment, the two Coherent sources are
obtained by,
a) refraction
b) reflection

4. c) internal reflection
2) Ionization Potential of Mercury
experiment
MCQ’S
1) The ionization potential of mercury is approximately
a) 5.4 V
b) 8.4 V
c) 10.4 V
d) 16.4 V
2) The advantage of mercury arc rectifier is that,
a) it has high efficiency
b) It has high overload capacity
c) it is comparatively noiseless
d) all of the above
3) A mercury arc rectifier possesses____ regulation characteristics
a) straight line
b) curved line
c) exponential
d) none of the above
4) The potential drop in the arc, in a mercury arc rectifier, varies
a) 0.05 V to 0.2 V per cm length of the arc
b) 0.5 V to 1.5 V per cm length of the arc
c) 2V to 3.5V per cm length of the arc
d) none of the above
5) In a mercury pool rectifier, the voltage drop across its electrodes
a) is directly proportional to load
b) is inversely proportional to load
c) varies exponentially with the load current

5. d) is almost independent of load current
Short questions;
1) write down the apparatus IPOM?
Answer; A gas-filled (mercury vapor) diode, a D.C. power supply, a
voltmeter, a millimeter, and connecting wires.
2) What is called phantom or thyratron?
Answer ; A diode filled with gas is called a phantom (or thyratron)
3) In which factors electronic current depends?
Answer ;
i. The number of electrons emitted per area from the cathode.
ii. The temperature of the cathode that you are providing by the
filament.
4) What is space charge and how to neutralize that?
Answer; When we increase the potential electrons get
accelerated and ionize the mercury atoms. As a result, we observe
the remaining positive ions near the anode plate. This ion charges
block the current. So further when we increase the potential it
moves towards the cathode plate and neutralizes the space
charge.
5) What is the ionization potential of mercury?
Answer ; For mercury, ionization potential is 10.39 V