- Amaterial medium
- Bvacuum
- Coscillating electric and magnetic fields
- Doscillating electric and magnetic fields whose directions are perpendicular to each other
Explanation:
Electromagnetic waves travel through oscillating electric and magnetic fields whose directions are perpendicular to each other.
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If in a plano-convex lens, the radius of curvature of the convex surface is 10 cm and the focal length of the lens is 30 cm, then the refractive index of the material of lens will be
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(a) 1.5 |
(b) 1.66 |
(c) 1.33 |
(d) 3 |
Which one of the following is true in photoelectric emission
|
(a) Photoelectric current is directly proportional to the amplitude of light of a given frequency |
|
(b) Photoelectric current is directly proportional to the intensity of light of a given frequency at moderate intensities |
|
(c) Above the threshold frequency, the maximum K.E. of photoelectrons is inversely proportional to the frequency of incident light |
|
(d) The threshold frequency depends upon the wavelength of incident light |
Electric charge is uniformly distributed along a long straight wire of radius 1mm. The charge per cm length of the wire is Q coulomb. Another cylindrical surface of radius 50 cm and length 1m symmetrically encloses the wire as shown in the figure. The total electric flux passing through the cylindrical surface is

|
(a) |
(b) |
(c) |
(d) |
Two metal spheres of capacitance
and
carry some charges. They are put in contact and then separated. The final charges
and
on them will satisfy
|
(a) |
(b) |
(c) |
(d) |
The potential at a point, due to a positive charge of 100μC at a distance of 9m, is
|
(a) |
(b) |
(c) |
(d) |
In the lowest energy level of hydrogen atom, the electron has the angular momentum
|
(a) |
(b) h/ |
(c) h/2 |
(d) |
Red light is used as danger signal because it is:
In electrolysis, if the duration of the passage of current is doubled, the mass liberated i
|
(a) Doubled |
(b) Halved |
(c) Increased four times |
(d) Remains the same |