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801.

In a compound microscope, maximum magnification is obtained when the final image (a) is formed at infinity (b) is formed at the least distance of distinct vision (c) coincides with the object (d) coincides with the objective lens

Answer»

Correct Answer is: (b)
Discussion
802.

In a compound microscope, maximum magnification is obtained when the final imageA. is formed at infinityB. is formed at the least distance of district visionC. coincies with the objectD. coincides with the objective lens

Answer» Correct Answer - B
Discussion
803.

If `epsi_(0)` and `mu_(0)` are respectively, the electric permittivity and the magnetic permeability of free space, `epsi` and `mu` the corresponding quantities in a medium, the refractive index of the medium isA. `(epsilon mu)/(epsilon_(0)mu_(0))`B. `((epsilon mu)/(epsilo_(0)mu_(0)))^(1//2)`C. `((epsilon_(0)mu_(0))/(epsilon mu))`D. `((epsilon_(0)mu_(0))/(epsilon mu))^(1//2)`

Answer» Correct Answer - B
Discussion
804.

At what magnification `T` of a telescope with a diameter of the objective `D = 6.0 cm` is the illuminance of the image of an object on the retina not less than without the telescope ? The pupil diameter is assumed do be equal to `d_(0) = 3.0 mm`. The losses of light in the telescope are negligible.

Answer» If `L` is the luminance of the object, `A` is its area, `s =` distance of the object then light falling on the objective is
`(Lpi D^(2))/(4s^(2)) A`
The area of the image formed by the telescope (assuming that the image concides with the object) is `T^(2) A` and the area of the final image on the retina is
`= ((f)/(s))^(2) T^(2) A`
Where `f =` focal length of the eye lens. thus the illuminance of the image on the retain (when the object is observed thorugh the telescope) is
`(LpiD^(2)A)/(4u^(2) ((f)/(s))^(2)T^(2)A) = (Lpi D^(2))/(4f^(2)T^(2))`
When the object is viewed directly, the illuminance is, similarly, `(L pi d_(0)^(2))/(4f^(2))`
We want `(L pi D^(2))/(4f^(2)T^(2)) ge (Lpid_(0)^(2))/(4f^(2))`
So, `T le (D)/(d_(0)) = 20` on substituation of the values.
Discussion