Home
Class 12
PHYSICS
An astronomical telescope has objective ...

An astronomical telescope has objective and eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective and the image is formed at infinity , the lenses must be separated by a distance

A

46 cm

B

50 cm

C

54 cm

D

37.3 cm

Text Solution

Verified by Experts

The correct Answer is:
The option C is correct.
Focal length of objective , `f_o=40` cm , focal length of eyepiece , `f_e =4 cm ` and distance of the object from the objective , `u_o =-200 cm.`

Let, distance of image from the objective `=v_o`
`therefore 1/(v_o)-1/(u_o)=1/(f_o) or, 1/(v_o)+1/(200)=1/(40) or, 1/(v_o)=1/(40)-1/(200) or, v_o=50 cm `
If distance between the eyepiece and the image formed by the objective is `u_e` , distance of the objective from the image is `v_e` and the image is formed at infinity,
`1/(v_e)-1/(u_e)=1/(f_e) or, 1/(oo)-1/(u_e)=1/4 or, u_e=-4 cm `
Therefore, the distance between the eyepiece and the objective ,`L=|v_o|+|u_e|=50+4=54 cm `
Promotional Banner

Topper's Solved these Questions

  • OPTICAL INSTRUMENTS

    CHHAYA PUBLICATION|Exercise CBSE SCANNER|8 Videos

  • OPTICAL INSTRUMENTS

    CHHAYA PUBLICATION|Exercise ENTRANCE CORNER ( Integer answer type )|2 Videos

  • Magnetic Properties of Materials

    CHHAYA PUBLICATION|Exercise CBSE SCANNER|11 Videos

  • QUANTUM THEORY

    CHHAYA PUBLICATION|Exercise CBSE Scanner|29 Videos

Similar Questions

Explore conceptually related problems

An astronomical refractive telescope has an objective of focal length 20 m and an eyepiece of focal length 2 cm .

The focal lengths of the objective and the eyepiece of an astronomical telescope are 140 cm and 5 cm respectively. The magnifying power of the telescope for viewing objects when the final image is formed at the least distance of distinct vision (25 cm ) will be

A small astronomical telescope has an objective of focal length 50 cm and an eyepiece of focal length 5 cm . It is focussed at the sun and the final image is formed at a distance of 25 cm from the eyepiece . If the diameter of the sun subtends an angle of 32' at the centre of the objective calculate the angular magnification of the instrument and the actual size of the image.

The focal lenghts of the objective and the eyepiece of a compound microscope are 2 cm and 10 cm respectively . At what distance from the objective must an object be placed so that the final image will be formed at infinity ? The distance between the two lenses is 16 cm .

In an astronomical telescope, focal length of the objective is made

The focal lengths of the objective and the eyepiece of an astronomical telescope are 140 cm and 5 cm respectively. (ii) When the telescope is in normal adjustment (i.e the final image is formed at infinity ), the magnifying power of the telescope will be

The focal lengths of the objective and the eyepiece of a compound microscope are 1 cm 5 cm respectively. If an object is placed at a distance of 1.1cm from the objective the final image is formed at a distance of 25 cm from the eyes. Determine the magnification and the distance between the lenses.

In an astronomical telescope , focal length of the objective is made

The focal lengths of the objective and the eyepiece of a compound microscope are 4mm and 25 mm respectively . The length of the tube of the instrument is 16 cm . If the final image is formed at infinity and the least distance of distinct vision is 25 cm , determine the magnifying power of the instrument .

The focal lengths of the lenses of the objective and eyepiece of a microscope are 2 cm and 5 cm respectively. The distance between them is 20 cm . At what distance from the objective should the object be placed so that the final image is formed 25 cm from the eyepiece ? what will be the magnification ?