Chapter 9 – Ray Optics and Optical Instruments

Fig. shows an equiconvex lens (of refractive index 1.5) in contact with a liquid layer on top of a plane mirror. A small needle with its tip on the principal axis is moved along the axis until its inverted image is found at the position of the needle. The distance of the needle from the [...]

Light incident normally on a plane mirror attached to a galvanometer coil retraces backwards a shown in Fig. A current in the coil produces a deflection of 3.5^∘ in the mirror. What is the displacement of the reflected spot of light on a screen placed 1.5 m away ? A screen is placed 90 cm [...]

A Cassegrainian telescope uses two mirrors as shown in Fig. Such a telescope is built with the mirrors 20 mm apart. If the radius of curvature of large mirror is 220 mm and the small mirror is 140 mm, where will the final image of an object at infinity be ? A Cassegrainian telescope uses [...]

At what angle should a ray of light be incident on the face of a prism of refracting angle 60^∘ so that it just suffers total internal reflection at the other face? The refractive index of the material of the prism is 1.524. A screen is placed 90 cm from an object. The image an [...]

(a) For the telescope described what is the separation between the objective lens and eye piece ? (b) If this telescope is used to view a 100m tall tower 3km away, what is the height of the image of the tower formed by the objective lens ? (c ) What is the height of the [...]

A small telescope has an objective lens of focal length 140cm and eye piece of focal length 5.0cm. What is the magnifying power of telescope for viewing distant objects when (a) the telescope is in normal adjustment (i.e. when the image is at infinity) (b) the final image is formed at the least distance of [...]

An angular magnification (magnifying power) of 30 X is desired using an objective of focal length 1.25 cm and an eye piece of focal length 5 cm. How will you set up the compound microscope ? An angular magnification (magnifying power) of 30 X is desired using an objective of focal length 1.25 cm and [...]

(i) At what distance should the lens be held from the card sheet in order to view the squares distinctly with the maximum possible magnifying power ? (ii) What is the magnification in this case ? (iii) Is the magnification equal to magnifying power in this case ? Explain. A screen is placed 90 cm [...]

A cardsheet divided into squares each of size 1mm2 is being viewed at a distance of 9cm through a magnifying glass (a converging lens of focal length 10cm) held close to the eye. (a) What is the magnification produced by the lens ? How much is the area of each square to the virtual image [...]

A myopia person has been using spectacles of power −1.0 dioptre for distant vision. During old age, he also needs to use separate reading glasses of power +2.0 dioptre. Explain what may have happened. A myopia person has been using spectacles of power −1.0 dioptre for distant vision. During old age he also needs to [...]