# HSC Physics board paper solution 2020

HSC Physics Paper board Solution 2020 of class 12Â  with complete explanation.

HSC Physics board paper solution for class 12 24th feb 2020

For Physics Question Paper refer “hsc 2020 physics board question paper” of class 12.

How to Pass in Physics Board Exam some Important Questions Paper-1 click to Refer

Physics Paper 2 Important Questions to refer before exam Click to read

Answers for HSC Physics board Paper MCQs Solution 2020 class 12 with explanation below…

## SECTION – A

Q1. Select and write correct answers of the following questions:

1. If length of a potentiometer wire is increased by keeping constant potential difference across the wire, then _______

a) Null point is obtained at larger distance

b)There is no change in the null point

d)Null point is obtained at shorter distance

Ans : a) Null point is obtained at larger distance

2.If a coil of metal wire is kept stationary in a uniform magnetic field, then _______

a) An e.m.f is induced in the coil

b) A current is induced in the coil

c) Neither e.m.f, nor current is induced

d) Both current and e.m.f. are induced

Ans : c) Neither e.m.f, nor current is induced

Explanation :-  If coil of metal wire at stationary means at rest position which equals zero, then nothing happens that means no current and e.m.f induced..

3.In rotational motion of a rigid body, all particles move with _______

a) Same linear velocity and same angular velocity

b) Same linear velocity and different angular velocity

c) different linear velocity and same angular velocity

d) different linear velocity and different angular velocity

Ans: c) different linear velocity and same angular velocity

4.A standing wave is produced on a string fixed at one end and free at other end. The length of string must be an _______

a) Odd integral multiple of Î»/4

b) Integral multiple of Î»/2

c) Integral multiple of Î»

d) Integral multiple of Î»/4

Ans: a) Odd integral multiple of Î»/4

5.Herapathite (iodo sulphate of quinine) is used in the production of _____

a) Achromatic prism

b) Polaroid

c) Biprism

d) Solar cell

Ans: b) Polaroid

Explanation –  Herapathite, or iodoquinine sulfate, is a chemical compound whose crystals are dichroic and thus can be used for polarizing light. …(refer for same https://en.wikipedia.org/wiki/Herapat…) first line..

6.A diffraction pattern is obtained by making blue light incident on a narrow slit . If blue light is replaced by red light, then the diffraction bands _______

a) Disappear

c) Become narrower

d) Remain same

7.Two droplets coalesce in a single drop. In this process _______

a) Energy is liberated

b) Energy is absorbed

c) Energy does not change

d) Some mass is converted into energy

Ans : – a) Energy is liberated

Explanation. In textbook at end of chapter 6th  in summary section 9th point there is clearly mentioned that.. If number of liquid droplets are merged to form a single drop then its surface area decreases, surface energy decreases, temperature of liquid increases and energy is liberated… hope u got your answer…

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8.In hydrogen atom, electron jumps from the 3rd orbit to 1st orbit. The change in angular momentum is ______________

a) 1.05 * 10-34 Js

b) 2.11 * 10-34 Js

c) 3.16 * 10-34 Js

d) 4.22 * 10-34 Js

Ans : b) 2.11 * 10-34 Js

Explanation .. as for nth orbit , angular momentum = nh/2Ï€ so for 1st orbit it will be = (1)h/2Ï€—- n value is 1 for 3rd orbit it will be =(3)h/2Ï€. So change ofangular momentum from 3rd orbit to 1st orbit will be = [(3h/2Ï€)-(h/2Ï€)] =2h/2Ï€ =h/Ï€ =[(6.63 * 10-34 )/3.142] = 2.11 * 10-34 Js

9.A fixed volume of iron is drawn into wire of length â€˜Lâ€™ the extension â€˜xâ€™ produced in the wire by a constant force â€˜Fâ€™ is proportional to _____________

a) 1/L2

b) 1/L

c) L2

d) L

Ans : c) L2

Explanation:  Y= FL/Al

l=FL/YA

l=FL2/Y (AL)

l=F L2/YVâ€¦ as volume=A*L as elongation x could be= l

x=F L2/VYâ€¦so by all constants we get F, V, Y x directly to L2

10.Two tuning forks have frequencies 450Hz and 454hz resp. on sounding these forks together, the time interval between two successive maximum intensities will be _____

a) 1\4s

b) 1/2s

c) 1s

d) 4s

Ans: a) 1/4s

Explanation u know that theory says that the time interval between two successive maxima of sound is always = [1/(n1-n2)] =[1/(454-450)] =1/4s

1. What is attenuation in communication system?

Ans : The loss or reduction of strength of a signal(Digital or Analog) while propagating through a medium is known as attenuation.

2. What is Isothermal process?

Ans : A process in which the temperature of the system is kept fixed throughout is called as isothermal process.

Ans : ve sign indicates the induced e.m.f. opposes the change in the magnetic flux.

4. Define Uniform Circular Motion ?

Ans: The Motion of a particle along circumference of circle with constant speed is U.C.M

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5. At which position, the total energy of a particle executing linear S.H.M is purely potential?

Ans: Extreme Position

6. State the name of the visible series in hydrogen spectrum?

And: Balmer Series.

7 At what height the acceleration due to gravity is 25% of that at the surface of the earth in term’s of radius of the Earth?

Ans: At h=R.

8. Capacity of a parallel capacitor with dielectric constant 5 is 40microfarad. Calculate the capacity of the same capacitor when dielectric material is removed.

Ans.

Cmedium = 40ÂµF

k=5

Cair   = Cmedium/k

= 40ÂµF/5

=8ÂµF.

Ans . Cair   = 8ÂµF

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## SECTION-B

Attempt any Eight questions of the following

Q.3. Define.

a) Threshold Frequency-

The Minimum frequency of incident radiation for which photo-electrons are emitted from photo-sensitive material is called threshold frequency.

b) Photo-Electric Work Function-

The Minimum energy required to free the electron from an atom of a given surface is called as photo-electric work function.

Q4. Distinguish Between Step-Up and Step-Down Transformer?

Ans.

Step-Up Transformer

1. In Step-Up Transformer Input Voltage is low while while the Output Voltage is high.
2. Step-Up Transformer’s Primary windings are made up of thick insulated copper wire.
3. Step-up transformer is used to increase the output voltage.
4. Rating of output voltage is 10000 volts.
5. Applications of Step-up tansformer are X-ray machines, microwaves.

Step-down Transformer

1. In step-down transformer Output voltage is low while the input voltage is high.
2. Step-down Transformer’s Secondary windings are made up of thick insulated copper wire.
3. Step-down transformer is used to reduce the output voltage.
4. Rating of output voltage is 110 volts.
5. Applications of step-down transformer are door-bell, voltage converter.

Q5. Write a note on Sky Wave Propagation?

Ans. When antenna transmits the radio-waves through sky, to reach the receiving antenna after reflection in the ionosphere region this wave propagation is called as sky wake propagation.

In Sky wave propagation, the maximum angle made by transmitted radio waves with horizontal, above which the radio waves are no longer reflected back by ionosphere is called angle of radiation.

Q6.Obtain the relation between the magnitude of linear acceleration and angular acceleration in circular motion?.

&

Q7. Deduce Boyle’s Law using the expression for pressure exerted by the gas.

Q8. State any two postulate’s of Bohr’s Theory of Hydrogen Atom?

Ans. i) The electron in a hydrogen atom revolves in circular orbit around the nucleus which is at te centre of orbit.

ii) The electron revolves around the nucleus in orbits of which electron’s angular momentum in the orbit is quantized.

Q9. State the factors on which resolving power of microscope depends. How it can be increased?

Ans Resolving power of a micro- scope depends on mode of illumination in which-

(a) wavelength of light (Î»)

(b) the semi-vertical angle of the cone of light from the object to the objective i.e Numerical Aperture(NA).

And to increase the resolving power of microscope you have to increase its numerical aperture(NA) and decrease the wavelength(Î») of light being illuminated.

Q10.

Q13.

14.

SECTION – C

Attempt any Eight questions of the following

Q 15.

Remaining updating in a short while after some time â€¦.

if you have any query then pls let me know in the comment box.. your suggestions are welcome…

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