A convex and concave lens of focal length f are in contact the focal length of the combinations will be
1.zero
2.f / 2
3.2f
4.infinite
Posted Date:-2021-08-26 22:11:52
A convex lens acts as a diverging lens if the
1.object is beyond C
2.if the object is with in C
3.if the object is within f
4.both (b) and (c)
Posted Date:-2021-08-26 22:11:52
A convex lens gives a virtual image only when the objects lies
1.between principal focus and center of curvature
2.beyond 2 f
3.at the principal focus
4.between principal focus and optical center
Posted Date:-2021-08-26 22:11:52
A convex lens of focal length f1 and a concave lens of focal length f2 are placed in contact. The focal length of the combination is
1.f2 + f1
2.f2 - f1
3.f1f2/f2+f1
4.f1f2/f1-f2
Posted Date:-2021-08-26 22:11:52
A lens which converges a beam of parallel rays to a point is called
1.diverging (or concave) lens
2.converging (or convex) lens
3.plano concave lens
4.plano convex lens
Posted Date:-2021-08-26 22:11:52
A lens, which is thicker at the center and thinner at the edges is called
1.concave lens
2.convex lens
3.plano convex lens
4.plano concave lens
Posted Date:-2021-08-26 22:11:52
A point where the incident parallel rays of light converge or appear to diverge after passing through a lens is called
1.center of curvature
2.focus
3.optical center
4.aperture
Posted Date:-2021-08-26 22:11:52
A spectrometer is used to find
1.wave length of light
2.refractive index of the prism
3.wavelength of different colours
4.all of the above
Posted Date:-2021-08-26 22:11:52
A wire having very high value of conductance is said to be
1.very good conductor
2.moderately good conductor
3.an insulator
4.no specific criterion available
Posted Date:-2021-08-26 22:11:52
A wire of uniform area of cross-section A length L and resistance R is cut into two parts. Resistivity of each part
1.remains the same
2.is doubled
3.is halved
4.becomes zero
Posted Date:-2021-08-26 22:11:52
Critical angle is that incident angle in denser medium for which angle of refraction is
1.0?
2.45?
3.90?
4.180?
Posted Date:-2021-08-26 22:11:52
Dioptre power of an concave lens of 10 cm focal length is
1.10 dioptre
2.10 dioptre
3.1 / 10 dioptre
4.1 / 10 dioptre
Posted Date:-2021-08-26 22:11:52
Dispersional effect may produce error in light signals. This type of error
1.single mode step index fibre
2.multimode step index fibre
3.multimode graded index fibre
4.monomode step index fiber
Posted Date:-2021-08-26 22:11:52
Errors in the transmission of power through optic fiber can be minimized by using a
1.Multimode index fiber
2.Graded index fiber
3.Single mode step index fiber
4.Copper wire
Posted Date:-2021-08-26 22:11:52
Final image produced by a compound microscope is
1.real and inverted
2.real and erect
3.virtual and erect
4.virtual and inverted
Posted Date:-2021-08-26 22:11:52
For normal adjustment, length of astronomical telescope is
1.fo + fe
2.fo - fe
3.fo / fe
4.fe / fo
Posted Date:-2021-08-26 22:11:52
How much heat does a 40 W bulb generates in one hour?
1.144000J
2.144J
3.1.44J
4.14J
Posted Date:-2021-08-26 22:11:52
If a convex lens of focal length f is cut into two identical halves along the lens diameter the focal length of each half is
1.f
2.f/2
3.2f
4.3f/2
Posted Date:-2021-08-26 22:11:52
If a convex lens of large aperture fails to converge the light rays incident on it to a single point, it is said to suffer from
1.chromatic aberration
2.spherical aberration
3.both spherical and chromatic
4.distortion
Posted Date:-2021-08-26 22:11:52
If an object is placed away from 2f of a converging lens then the image will be
1.real and erect
2.virtual and erect
3.real and inverted
4.virtual
Posted Date:-2021-08-26 22:11:52
Image of an object 5 mm high is only 1 cm high. Magnification produced by lens is
1.0.5
2.0.2
3.1
4.2
Posted Date:-2021-08-26 22:11:52
In going form a denser to rarer medium a ray of light is
1.undeviated
2.bent away form the normal
3.bent towards the normal
4.polarized
Posted Date:-2021-08-26 22:11:52
In multimode step index fibre the refractive index of core and cladding is
1.same
2.different
3.zero
4.different with refractive index of core higher than cladding
Posted Date:-2021-08-26 22:11:52
In optic fiber transmission system __________ are used regenerate the dim light signal.
1.Diodes
2.Repeaters
3.Laser
4.Transformer
Posted Date:-2021-08-26 22:11:52
In optic fiber transmission the repeater are separated through a distance of ______ km in newer system.
1.300km
2.200km
3.100km
4.20km
Posted Date:-2021-08-26 22:11:52
Least distance of distinct vision
1.increases with increase in age
2.decreases with increase in age
3.neither increases nor decreases
4.becomes infinite after 60 years
Posted Date:-2021-08-26 22:11:52
Light signals passes through multimode graded index fibre due to
1.continuous refraction
2.total internal reflection
3.both continuous refraction and total internal reflection
4.diffraction
Posted Date:-2021-08-26 22:11:52
Magnification of the astronomical telescope is
1.fo+fe
2.fo/fe
3.fe/fo
4.(1+fo/fe)L/fo
Posted Date:-2021-08-26 22:11:52
Magnifying power of simple microscope
1.increase with increase in focal length
2.increase with decrease in focal length
3.no effect with decrease or increase with focal length
4.list distance of distinct vision
Posted Date:-2021-08-26 22:11:52
Michelson calculated the speed of light using the instruments
1.spectrometer
2.galvanometer
3.interferometer
4.none of these
Posted Date:-2021-08-26 22:11:52
Michelson devised the formula to calculate the speed of light
1.C = 4fd
2.C = 8fd
3.C = 16fd
4.C = 5/2fd
Posted Date:-2021-08-26 22:11:52
One kilowatt hour is the amount of energy delivered during
1.one second
2.one day
3.one minute
4.one hour
Posted Date:-2021-08-26 22:11:52
Production of heat due to an electric current flowing through a conductor is given by
1.Joule effect
2.Joule Thomsons effect
3.Comptons effect
4.Feed back effect
Posted Date:-2021-08-26 22:11:52
Resistance of a conductor depends upon
1.nature of conductor
2.dimension of conductor
3.physical state of the conductor
4.all of above
Posted Date:-2021-08-26 22:11:52
The current through a metallic conductor is due to the motion of
1.free electrons
2.protons
3.neutrons
4.still under controversy
Posted Date:-2021-08-26 22:11:52
The diameter of a lens is called
1.focal length
2.principal axis
3.aperture
4.radius of curvature
Posted Date:-2021-08-26 22:11:52
The electrical signals change into light signals for transmission through optical fibre. A light pulse represent
1.zero (0)
2.One (1)
3.both zero (0) and one (1)
4.neither zero (0) nor one (1)
Posted Date:-2021-08-26 22:11:52
The equation ?min = 1.22 ?/D was devised by
1.Newton
2.Einstein
3.Raleigh
4.Planks
Posted Date:-2021-08-26 22:11:52
The function of collimeter in spectrometer is
1.to produce parallel beams of light
2.to filter the light rays
3.to make them
4.no function
Posted Date:-2021-08-26 22:11:52
The least distance of distinct vision for a normal eye is
1.15 cm
2.25 cm
3.30 cm
4.40 cm
Posted Date:-2021-08-26 22:11:52
The minimum distance between an object and its real image in a convex lens is
1.2 f
2.2.5 f
3.3f
4.4f
Posted Date:-2021-08-26 22:11:52
The power of a concave lens is
1.real
2.virtual
3.positive
4.negative
Posted Date:-2021-08-26 22:11:52
The value of critical angle for glass is
1.42?
2.47?
3.52?
4.50?
Posted Date:-2021-08-26 22:11:52
There is no noticeable boundary between core and cladding
1.multi mode step index fibre
2.multi mode graded index fibre
3.single mode step index fibre
4.all types of fibre
Posted Date:-2021-08-26 22:11:52
Thermocouples convert
1.heat energy into electrical energy
2.heat energy into light energy
3.heat energy into mechanical energy
4.mechanical energy into heat energy
Posted Date:-2021-08-26 22:11:52
Three equal resistors connected in series with a source of e m f together dissipate 10 W of power each. What will be the power dissipated if the same resistors are connected in parallel across the same source of e m f?
1.40 W
2.90W
3.100W
4.120W
Posted Date:-2021-08-26 22:11:52
Two convex lenses of equal focal length f are placed in contact the resultant focal length of the combination is
1.zero
2.focus
3.2 f
4.f/2
Posted Date:-2021-08-26 22:11:52
Unit of power of a lens is
1.meter
2.watt
3.dioptre
4.horsepower
Posted Date:-2021-08-26 22:11:52
When same current passes for same time through a thick and thin wire
1.more heat is produced in thick wire
2.more heat is produced in thin wire
3.no heat is produced in wire
4.less heat is produced in thick wire
Posted Date:-2021-08-26 22:11:52
Which one type of fibre is more suitable for transmission of signals in which white light is used ?
1.mono mode step index fibre
2.multi mode step index fibre
3.multi mode graded index fibre
4.single mode step index fibre
Posted Date:-2021-08-26 22:11:52