# Viva questions for Physics Practical | Class 12

MAGNETS

Q.1. What do you mean by declination?
Ans: The angle between the magnetic meridian at a place and geographic meridian at that place is called magnetic declination. It varies from place to place on the surface of the earth.

Q.2. Can you measure the declination for this place here in the laboratory?
Ans: Yes, the angle between the compass needle and the geographic meridian gives the declination.

Q.3. What do you mean by dip?
Ans: The angle that the direction of earth’s magnetic field makes with the horizontal at a place is called dip at that place.

Q.4. Where is the value of dip maximum/minimum?
Ans: Dip is maximum at the poles (900) and minimum at the equator (00).

Q.5. Why do you align the bar magnet in the N-S direction of Earth?
Ans: So that while tracing the magnetic field lines of the bar magnet we do not get any irregular shape due to the interaction of Earth’s magnetic field with the bar magnet.

Q.6. What is the neutral point?
Ans: A neutral point is that point where the field due to a magnet is completely neutralized by the horizontal component of the earth’s magnetic field.

Q.7. What do you mean by magnetic and geometric length of a bar magnet?
Ans: The physical length of a bar magnet is called its geometric length.
The actual distance between the poles of a magnet is called its magnetic length.

Q.8. What should be the value of the ratio magnetic length / Geometric length of a bar magnet?
Ans: 0.86 (approx.)

Q.9. What is the direction of the magnetic field lines?
Ans: From North to South

Q.10. Why do we use brass pins for fixing the paper on the table?
Ans: Because brass is non-magnetic.

GLASS SLAB and PRISM

Q.1. What do you mean by refraction?
Ans: The bending of light in traveling from one medium to another is called refraction.

Q.2. What is refractive index?
Ans: The ratio of velocity of light in one medium to the velocity of light in the other is called refractive index.

Q.3. What is the angle between the incident and emergent ray in case of parallel glass slab?
Ans: 00

Q.4. Do frequency of white light change during refraction in a glass slab?
Ans: No

Q.5. What is angle of deviation of a prism?
Ans: The angle between the incident ray and emergent ray.

Q.6. What is minimum deviation?
Ans: That particular value of angle of deviation for which the angle of incidence is equal to the angle of emergence is called the angle of minimum deviation. At this condition, the refracted ray inside the prism is parallel to the base?

Q.7. How many refractions take place in a prism?
Ans: Two

Q.8. Can prism act as glass slab?
Ans: Yes, during the condition of minimum deviation.

Q.9. What is dispersion?
Ans: The splitting of white color into its constituent colors is called dispersion.

Q.10. What do you mean by angle of prism?
Ans: The angle between the two refracting surfaces of a prism.