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 Bihar Board 12th Physics Objective Important Questions Part 3

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
Answer:
(ii) 90°

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

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

Question 5.
When the magnetic moment increases, time period?
(i) increases
(ii) decreases
(iii) remains unchanged
(iv) None of these
Answer:
(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
Answer:
(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) 1F2
(iv) 4F
Answer:
(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
Answer:
(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) f2
(iv) 3f
Answer:
(iii) f2

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

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

Question 12.
The focal length of a lens is f meter. Its power is:
(i) f dioptre
(ii) 1f dioptre
(iii) 1f2 dioptre
(iv) f2 dioptre
Answer:
(ii) 1f dioptre

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

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

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

Question 17.
Air bubble inside water seems to glow due to:
(i) reflection
(ii) refraction
(iii) diffraction
(iv) Total intend reflection
Answer:
(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
Answer:
(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
Answer:
(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
Answer:
(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
Answer:
(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
Answer:
(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) m1m2
(iv) m1m2
Answer:
(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
Answer:
(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.
Answer:
(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
Answer:
(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
Answer:
(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
Answer:
(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
Answer:
(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
Answer:
(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
Answer:
(iv) Bifocal lens

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

Question 35.
Images of an object exists in brain in persistance of vision for:
(i) 120 sec.
(ii) 110 sec.
(iii) 20 sec.
(iv) 10 sec.
Answer:
(ii) 110 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
Answer:
(i) red

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

Question 38.
Spectrum of star is:
(i) continuous
(ii) line
(iii) dark line spectrum
(iv) band
Answer:
(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
Answer:
(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
Answer:
(i) Absorption of light in chromosphere

Question 41.
Fresnel distance zf is equal to
(i) a/λ
(ii) a2λ
(iii) λa
(iv) λa2
Answer:
(ii) a2λ

Question 42.
Line spectra is obtained in:
(i) Atomic state
(ii) Molecular state
(iii) Gaseous state
(iv) Liquid state
Answer:
(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
Answer:
(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
Answer:
(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
Answer:
(ii) (µ – 1)A

Question 46.
Red colour of sunrise and sunset is due to:
(i) polarisation of light
(ii) colour of sun
(iii) scattering of light
(iv) colour of sky
Answer:
(iii) scattering of light