# Bihar Board 12th Physics Objective Important Questions Part 3

BSEB Bihar Board 12th Physics Important Questions Objective Type Part 3 are the best resource for students which helps in revision.

## Bihar Board 12th Physics Objective Important Questions Part 3

Question 1.
Tangent law is applicable between the two magnetic force when the angle between them is:
(i) 45°
(ii) 90°
(iii) 0°
(iv) None
(ii) 90°

Question 2.
Copper is:
(i) dia magnetic
(ii) ferro magnetic
(iii) para magnetic
(iv) None of the above
(i) dia magnetic

Question 3.
The permeability of a certain material is less than 1. Its susceptibility will be:
(i) positive and large
(ii) zero
(iii) positive and small
(iv) negative
(iv) negative

Question 4.
SI unit of magnetic pole strength is:
(i) N
(ii) N/Am
(iii) Am
(iv) T
(iii) Am

Question 5.
When the magnetic moment increases, time period?
(i) increases
(ii) decreases
(iii) remains unchanged
(iv) None of these
(ii) decreases

Question 6.
The apparent dip at a place is always:
(i) less than true dip
(ii) equal to the true dip
(iii) greater than the true dip
(iv) None of these
(iii) greater than the true dip

Question 7.
On dipping into water, the focal length (F) of lens becomes equal to:
(i) F
(2) 2F
(iii) $$\frac{1}{F^{2}}$$
(iv) 4F
(iv) 4F

Question 8.
Two lenses of focal length 20 cm. and -40 cm. are in contact. The power of combination will be:
(i) 5D
(ii) 2.5D
(iii) -2.5D
(iv) -5D
(ii) 2.5D

Question 9.
Two thin lenses (f) are in contact to each other. Their equivalent focal length will be:
(i) 2f
(ii) 4f
(iii) $$\frac{f}{2}$$
(iv) 3f
(iii) $$\frac{f}{2}$$

Question 10.
Power of a lens of focal length 10 cm. is:
(i) +5D
(ii) -5D
(iii) +10D
(iv) -10D
(iii) +10D

Question 11.
A convex lens is immersed in water. Its power:
(i) increases
(ii) decreases
(iii) remains constant
(iv) none of these
(ii) decreases

Question 12.
The focal length of a lens is f meter. Its power is:
(i) f dioptre
(ii) $$\frac{1}{f}$$ dioptre
(iii) $$\frac{1}{f^{2}}$$ dioptre
(iv) f2 dioptre
(ii) $$\frac{1}{f}$$ dioptre

Question 13.
Blue colour of sky is due to the phenomenon of
(i) Refletion
(ii) Refraction
(iii) Scattering
(iv) Dispersion
(iii) Scattering

Question 14.
The stars twinkle at night due to:
(i) reflection
(ii) diffraction
(iii) refraction
(iv) stars emitting energy
(iii) refraction

Question 15.
A bubble of air inside water appears shining due to:
(i) refraction
(ii) reflection
(iii) diffraction
(iv) total internal reflection
(iv) total internal reflection

Question 16.
When a beam of monochromatic light passes from one medium to another, the quantity that does not change?
(i) wave length
(ii) frequency
(iii) velocity
(iv) amplitude
(ii) frequency

Question 17.
Air bubble inside water seems to glow due to:
(i) reflection
(ii) refraction
(iii) diffraction
(iv) Total intend reflection
(iv) Total intend reflection

Question 18.
Bending of light from the edge of an obstacle is called:
(i) diffraction
(ii) dispersion
(iii) refraction
(iv) reflection
(i) diffraction

Question 19.
The bending of a ray of light when it passes from one medium to another medium is called:
(i) diffraction
(ii) dispersion
(iii) refraction
(iv) reflection
(iii) refraction

Question 20.
A virtual image larger than the object can be produced by:
(i) convex mirror
(ii) plane mirror
(iii) concave mirror
(iv) concave lens
(iii) concave mirror

Question 21.
The image formed by a simple microscope is:
(i) virtual and erect
(ii) virtual and inverted
(iii) real and erect
(iv) real and inverted
(i) virtual and erect

Question 22.
In a compound microscope, if f0 and fe represent the focal length of the objective and the eye piece respectively then:
(i) f0 > fe
(ii) fe > f0
(iii) f0 = fe
(iv) f0 = 2fe
(ii) fe > f0

Question 23.
The magnifying power of the objective of a microscope is m1 and that of eyepiece is m2. The magnifying power of the microscope is:
(i) m1 + m2
(ii) m1 – m2
(iii) $$\frac{m_{1}}{m_{2}}$$
(iv) m1m2
(iv) m1m2

Question 24.
When the length of the tube of a microscope is increased its magnifying power:
(i) increases
(ii) decreases
(iii) becomes zero
(iv) remains unchanged
(i) increases

Question 25.
The objective of an astronomical telescope must have:
(i) a high power
(ii) a long focal length
(iii) a high refractive index
(iv) a low refractive index.
(ii) a long focal length

Question 26.
In fig. there are two covex lenses L1 & L2 of focal length F1 & F2 respectively. The distance between L1 & L2 will be –

(i) F1
(ii) F2
(iii) F1 + F2
(iv) F1 – F2
(iii) F1 + F2

Question 27.
In an astronomical telescope, the final image obtained is:
(i) real and erect
(ii) real and inverted
(iii) virtual and erect
(iv) virtual and inverted
(iv) virtual and inverted

Question 28.
Eyes having short-sightedness defect can see clearly:
(i) object at infinity
(ii) object at far distance
(iii) near by object
(iv) All the objects
(iii) near by object

Question 29.
To remedy the long-sight defect, a person has to use:
(i) a concave lens
(ii) a cylindrical lens
(iii) a plane-concave lens
(iv) a convex lens
(iv) a convex lens

Question 30.
For normal eye, the least distance of distinct vision is:
(i) 100 cm
(ii) 50 cm
(iii) 250 cm
(iv) 25 cm
(iv) 25 cm

Question 31.
To cure old sight defect, it is needed:
(i) Concave lens
(ii) Convex lens
(iii) Cylindrical lens
(iv) Bifocal lens
(iv) Bifocal lens

Question 32.
To cure Astigmatism, it is needed:
(i) Convex lens
(ii) Concave lens
(iii) Cylindrical lens
(iv) Bifocal lens
(iii) Cylindrical lens

Question 33.
The defect in sight due to difference in curvature in the various surfaces of the cornea is called:
(i) myopia
(ii) hyper metropia
(iii) presbyopia
(iv) astigmatism
(iv) astigmatism

Question 34.
Images of an object formed at Ratina is:
(i) imaginary and erect
(ii) imaginary and inverted
(iii) real and inverted
(iv) real and erected
(iii) real and inverted

Question 35.
Images of an object exists in brain in persistance of vision for:
(i) $$\frac{1}{20}$$ sec.
(ii) $$\frac{1}{10}$$ sec.
(iii) 20 sec.
(iv) 10 sec.
(ii) $$\frac{1}{10}$$ sec.

Question 36.
When white light is passed through prism, the minimum deviation will takes place in:
(i) red
(ii) violet
(iii) yellow
(iv) green
(i) red

Question 37.
Wavelength of the colour is largest in:
(i) red
(ii) yellow
(iii) violet
(iv) green
(i) red

Question 38.
Spectrum of star is:
(i) continuous
(ii) line
(iii) dark line spectrum
(iv) band
(iii) dark line spectrum

Question 39.
The Image formed by objective of a compound microscope is:
(i) Virtual & dimineshed
(ii) Real & diminished
(iii) Real & large
(iv) Virtual & large
(iii) Real & large

Question 40.
Fraunhofer lines in solar spectra are produced due to:
(i) Absorption of light in chromosphere
(ii) Absorption of light in atmosphere
(iii) Cosmic rays
(iv) None of these
(i) Absorption of light in chromosphere

Question 41.
Fresnel distance zf is equal to
(i) a/λ
(ii) $$\frac{a^{2}}{\lambda}$$
(iii) $$\frac{\lambda}{a}$$
(iv) $$\frac{\lambda}{a^{2}}$$
(ii) $$\frac{a^{2}}{\lambda}$$

Question 42.
Line spectra is obtained in:
(i) Atomic state
(ii) Molecular state
(iii) Gaseous state
(iv) Liquid state
(i) Atomic state

Question 43.
A chromatic combination of two prisms gives:
(i) Deviation without angular dispersion
(ii) Angular dispersion without deviation
(iii) Neither angular dispersion nor deviation
(iv) None of these
(i) Deviation without angular dispersion

Question 44.
With rise in wave length of light, the refractive index of a transparent medium
(i) increases
(ii) decreases
(iii) remains unchanged
(iv) None of the above
(ii) decreases

Question 45.
Minimum deviation angle of a thin prism is:
(i) (µ – 1)A2
(ii) (µ – 1)A
(iii) (µ + 1)A
(iv) (1 – µ)A