Home
Class 12
PHYSICS
The focal lengths of the objective and e...

The focal lengths of the objective and eye piece of an astronomical telescope are `25 cm and 2.5 cm` respectively. The telescope is fucussed on an object `1.5 m` from objective, the final image being formed `25 cm` from eye of the observer. Calculate the length of the telescope.

Text Solution

Verified by Experts

Here, `f_(0) = 25 cm, f_(e) = 2.5 cm`.
`u_(0) = - 1.5 m = - 150 cm., v_(e) = - 25 cm, L = ?`
As `(1)/(v_(0)) - (1)/(u_(0)) = (1)/(f_(0))`
`:. (1)/(v_(0)) = (1)/(f_(0)) + (1)/(u_(0)) = (1)/(25) - (1)/(150) = (6 - 1)/(150)`
`v_(0) = (150)/(5) = 30 cm`
Again, as `(1)/(v_(e)) - (1)/(u_(e)) = (1)/(f_(e))`
`:. (1)/(u_(e)) = (1)/(v_(e)) - (1)/(f_(e)) = (1)/(-25) - (1)/(2.5)`
`= (-1 - 10)/(25) = (-11)/(25)`
`u_(e) = (- 25)/(11) = - 2.27 cm`
Length of telescope, `L = |v_(0)| + |u_(e)|`
`= 30 + 2.27 = 32.27 cm`
Promotional Banner

Topper's Solved these Questions

  • OPTICS

    PRADEEP|Exercise Very short answer question|5 Videos

  • OPTICS

    PRADEEP|Exercise very short answer questions|1 Videos

  • MAGNETIC EFFECT OF CURRENT AND MAGNETISM

    PRADEEP|Exercise Competition Focus (Multiple Choice Questions)|2 Videos

Similar Questions

Explore conceptually related problems

The focal lengths of the objective and the eye-piece of an astronomical telescope are 0.25 m and 0.025 m, respectively. The telescope is focussed on an object 5m from the objective, the final image being formed 0.25 m from the eye of the observer. Calculate the length of the telescope and its magnifying power.

The focal lengths of the objective and the eye-piese of an astronomical telescope are 0.25 m and 0.025 m, respectively. The telescope is focussed on an object 5 m from the objective, the final image being formed 0.25 m from the eye of the observer. Calculate the length of the telescope and its magnifying power. [Hint : Mag. power = v_(0)//u_(e) ]

The focal lengths of the objective and the eye-piece of an astronomical telescope are 0.25 m and 0.02m, respectively. The telescope is adjusted to view an object at a distance of 1.5 m from the objective, the final image being 0.25 m from the eye of the observer. Calculate the length of the telescope and the magnification produced by it.

The focal length of the objective and eyepiece of an astronomical telescope for normal adjustments are 50 cm and 5 cm. The length of the telescope should be:

Focal length of objective lens and eyepiece of an astronomical telescope are 200cm and 10cm respectively. The length of telescope for maximum magnification is nearly

The focal length of objecive and eye-piece of astronomical telescope are 2 m and 5 cm respectively. The magnifying power of telescop when final image is formed at infinity is

Focal length of objective and eye piece of telescope are 200 cm and 4 cm respectively. What is the length of telescope for normal adjustment?

In an astronomical telescope, the focal lengths of the objective and the eye piece are 100cm and 5cm respectively. If the telescope is focussed on a scale 2m from the objective, the final image is formed at 25cm from the eye. Calculate (i) the magnification and (ii) the distance between the objective and the eyepiece

The focal lengths of the objective and the eyepiece of an astronomical telescope are 40 cm and 5 cm respectively. It is focussed on a scale at a distance of 2 m. The final image is formed at infinity. What is the separation between the two lenses ?

The focal lengths of the objective and the eyepiece of an astronomical telescope are 20 cm and 5 cm respectively. If the final image is formed at a distance of 30 cm from the eye piece, find the separation between the lenses for distinct vision: