Advertisements
Advertisements
प्रश्न
A small telescope has an objective lens of focal length 150 cm and an eye piece of focal length 5 cm. If this telescope is used to view a 100 m high tower 3 km away, find the height of the final image when it is formed 25 cm away from the eye piece.
Advertisements
उत्तर
The formula for magnifying power is,
Magnifying power, `M = -f_0/f_e (1+f_e/D)`
where, f0 = Focal length of the objective = 150 cm
fe = Focal length of the eye-piece = 5cm
D = Least distance of distinct vision = 25 cm
`M = -150/5 xx (1+5/25) =-36`
`M =beta/alpha`
`M = tan beta/tan alpha`(As angles α and β are small)
`tan alpha =( \text{Height of object})/(\text { Distance of object from objective}) = H/u = 100/3000 = 1/30`
`M =tan beta/((1/30))`
`tan beta = (-36)/30`
`tan beta = (\text{Height of image})/(\text { Distance of image formation}) = (H')/D`
Thus,
`H' = (-36 xx 25)/30 = -30 cm`
Negative sign indicates that we get an inverted image.
APPEARS IN
संबंधित प्रश्न
Why should the objective of a telescope have large focal length and large aperture? Justify your answer.
Write two important advantages of reflecting telescope over a refracting telescope.
Define magnifying power of a telescope. Write its expression.
Draw a labeled ray diagram of a reflecting telescope. Mention its two advantages over the refracting telescope.
A giant refracting telescope at an observatory has an objective lens of focal length 15 m. If an eyepiece lens of focal length 1.0 cm is used, find the angular magnification of the telescope. If this telescope is used to view the moon, what is the diameter of the image of the moon formed by the objective lens? The diameter of the moon is 3.42 × 106 m and the radius of the lunar orbit is 3.8 × 108 m.
An astronomical telescope is to be designed to have a magnifying power of 50 in normal adjustment. If the length of the tube is 102 cm, find the powers of the objective and the eyepiece.
The eyepiece of an astronomical telescope has a focal length of 10 cm. The telescope is focussed for normal vision of distant objects when the tube length is 1.0. m. Find the focal length of the objective and the magnifying power of the telescope.
(i) What is meant by resolving power of a telescope?
(ii) State any one method of increasing the resolving power of an astronomical telescope.
Draw a ray diagram of a refracting astronomical telescope when final image is formed at infinity. Also write the expression for its angular magnification (magnifying power).
Draw a ray diagram of Astronomical Telescope for the final image formed at infinity
