Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
21. What is the difference of two close frequencies of superimposing waves known as?
[A] Transverse frequency
[B] Beat frequency
[C] Normal frequency
[D] Angular frequency
Show Answer
Correct Answer: B [Beat frequency]
Notes:
The difference of two close frequencies of superimposing waves known as Beat frequency. It is represented by vbeat and Its S.I unit is s-1.
22. Which of the following sound waves are used in echocardiography?
[A] Infrasonic
[B] Ultrasonic
[C] Between 20 Hz and 2000 Hz
[D] None of the above
Show Answer
Correct Answer: B [Ultrasonic]
Notes:
Ultrasonic waves are made to reflect from various parts of the heart and form the image of the heart. This technique is called ‘echocardiography’.
23. Which of the following is true about an adiabatic wall?
[A] it allows flow of heat from one system to another
[B] it allows flow of particles from one system to another
[C] it does not allow flow of heat from one system to another
[D] None of the above
Show Answer
Correct Answer: C [it does not allow flow of heat from one system to another]
Notes:
An adiabatic wall is an insulating wall (can be movable) that does not allow flow of energy (heat) from one to another.
24. Which of the following is the mirror formula?
[A] v + u =f
[B] 1/v + 1/u = 1/f
[C] 1/v + 1/u = f
[D] None of the above
Show Answer
Correct Answer: B [1/v + 1/u = 1/f]
Notes:
Mirror formula represents image distance (v), object distance (u) and focal length (f) of the mirror. The mirror formula is 1/v + 1/u = 1/f. In case of lens it is 1/v – 1/u = 1/f.
25. Which of the following cells is the basis of Non-rechargeable batteries?
[A] Galvanic cells
[B] Electrolytic cells
[C] Both a and b
[D] None of the above
Show Answer
Correct Answer: A [Galvanic cells]
Notes:
Non-rechargeable batteries are examples of Galvanic cells.
26. Which is the direction of magnetic field inside a magnet?
[A] from south pole to north pole
[B] from north pole to south pole
[C] from north pole till centre of the magnet
[D] None of the above
Show Answer
Correct Answer: A [from south pole to north pole]
Notes:
Inside the magnet, the direction of field lines is from its south pole to its north pole.
27. What is the relationship between the magnetisation of a paramagnetic material and the absolute temperature?
[A] they are directly proportional to each other
[B] they are inversely proportional to each other
[C] they are independent of each other
[D] None
Show Answer
Correct Answer: B [they are inversely proportional to each other]
Notes:
The magnetisation of a paramagnetic material is inversely proportional to the absolute temperature. This is known as Curie’s law.
28. What is the SI unit of radioactivity?
[A] Becquerel
[B] candela
[C] curie
[D] Henry
Show Answer
Correct Answer: A [Becquerel]
Notes:
The System International of units (SI system) uses the unit of Becquerel (Bq) as its unit of radioactivity. 1 Becquerel is simply equal to 1 disintegration or decay per second.
29. The sliding friction is _____ than the static friction.
[A] greater
[B] smaller
[C] Same
[D] double
Show Answer
Correct Answer: B [smaller]
Notes:
The sliding friction is less than static friction because of the interlocking of irregularities in the two surfaces. When the object starts sliding the contact points on its surface, do not get enough time to lock into the contact points on the floor.
30. Which of the following situations arises when a man circles round the earth in a satellite? (UPSC Prelims 1979).
[A] The mass of man becomes zero but weight remains constant
[B] The Mass of man remains constant but weight becomes zero
[C] Both mass and weight of the man remain constant
[D] Both mass and weight of the man remain zero
Show Answer
Correct Answer: B [The Mass of man remains constant but weight becomes zero]
Notes:
Mass is the amount of matter enclosed by a body so it can never change with displacement in a body. Weight is a force actually force due to gravity taking earth into consideration. Therefore outside earth this force is negligible. Hence weight is zero. As W=mg, where g is the force due to gravity. When ‘g’ is almost negligible or nil, weight becomes zero. Hence outside earth weight is zero while mass is constant.
