An object is placed first at infinity and then at 20 cm from the object side focal plane of the convex lens. The two images thus formed are 5 cm apart. The focal length of the lens is
|
(a) 5 cm |
(b) 10 cm |
(c) 15 cm |
(d) 20 cm |
(b) 10 cm
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$\overrightarrow{\text{F}}\times\overrightarrow{\text{a}}$
$\overrightarrow{\text{v}}\times\overrightarrow{\text{r}}$
$\overrightarrow{\text{a}}\times\overrightarrow{\text{r}}$
$\overrightarrow{\text{F}}\times\overrightarrow{\text{r}}$
An a-particle of 5 MeV energy strikes with a nucleus of uranium at stationary at an scattering angle of 180o. The nearest distance upto which a-particle reaches the nucleus will be of the order of
|
(a) 1 Å |
(b) |
(c) |
(d) |
What is the time taken (in seconds) to cross a glass of thickness 4 mm and μ = 3 by light
|
(a) 4 |
(b) 2 |
(c) 16 |
(d) 8 |
If the electric flux entering and leaving an enclosed surface respectively is 
and 
the electric charge inside the surface will be
|
(a) ( |
(b) ( |
(c) ( |
(d) ( |
If a slab of insulating material 4 
thick is introduced between the plates of a parallel plate capacitor, the separation between plates has to be increased by 3.5 to restore the capacity to original value. The dielectric constant of the material will be
|
(a) 6 |
(b) 8 |
(c) 10 |
(d) 12 |
