F.Sc ICS Notes: Physics XI: Chapter 10 Optical Instruments Numerical Problems

F.Sc ICS Notes: Physics XI: Chapter 10 Optical Instruments Numerical Problems 1st Year Physics Notes Online Taleem Ilm Hub

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Numerical Problem 10.1: A converging lens of focal length 5 cm is used as a magnifying glass. If the neat point of the observer is 25cm and the lens is held close to the eye. Calculate (i) the distance of the object from the lens. (ii) the angular magnification. What is the angular magnification when the final image is formed at infinity?

Numerical Problem 10.2: A telescope objective has focal length 96cm and diameter 12cm. Calculate the focal length and minimum diameter of a simple eye piece lens for use with the telescope, if the linear magnification required is 24 times and all the light transmitted by the objective from a distant point on the telescope axis is to fall on the eye piece.
Numerical Problem 10.3: A telescope is made up of an objective of focal length 20cm and an eye piece of 5cm, both are convex lenses. Find the angular magnification.

Numerical Problem 10.4: A simple astronomical telescope in normal adjustment has an objective of focal length 100cm and an eye piece of focal length 5cm. (i) Where is the final image formed? (ii) Calculate the angular magnification.
Numerical Problem 10.5: A point object is placed on the axis of 3.6cm from a thin convex lens of focal length 3cm. A second thin convex lens of focal length 16cm is placed coaxial with the first and 26cm from it on the side away from the object. Find the position of the final image produced by the two lenses.

Numerical Problem 10.6: A compound microscope has lenses of focal length 1cm and 3cm. An object is placed 1.2cm from the object lens. If a virtual image is formed, 25 cm from the eye, calculate the separation of the lenses and the magnification of the instrument.

Numerical Problem 10.7: Sodium light of wavelength 589nm is used to view an object under a microscope. If the aperture of the objective is 0.9cm, (i) find the limiting angle of resolution, (ii) using visible light of any wavelength, what is the maximum limit of resolution for this microscope.

Numerical Problem 10.8: An astronomical telescope having magnifying power of 5 consist of two thin lenses 24cm apart. Find the focal lengths of the lenses.

Numerical Problem 10.9: A glass light pipe in air will totally internally reflect a light ray if its angle of incidence is at least 39 degree. What is the minimum angle for total internal reflection if pipe is in water? (Refractive index of water = 1.33)

Numerical Problem 10.10: The refractive index of the core and cladding of an optical fiber are 1.6 and 1.4 respectively. Calculate (i) the critical angle for the interface (ii) the maximum angle of incidence in the air, of a ray, which enters the fiber and is incident at the critical angle on the interface.

Written by: Asad Hussain