NCERT Solutions for Class 12 Help.html Physics Part Ii Chapter 9 Ray Optics And Optical Instruments

Show using a proper diagram how unpolarised light can be linearly polarised by reflection from a transparent glass surface.

The figure shows a ray of light falling normally on the face AB of an equilateral glass prism having refractive index 3/2, placed in water of refractive index 4/3. Will this ray suffer total internal reflection on striking the face AC? Justify your answer.

A symmetric biconvex lens of the radius of curvature R and made of glass of refractive index 1.5, is placed on a layer of liquid placed on top of a plane mirror as shown in the figure. An optical needle with its tip on the principal axis of the lens is moved along the axis until its real, inverted image coincides with the needle itself. The distance of the needle from the lens is measured to be x. On removing the liquid layer and repeating the experiment, the distance is found to bey. Obtain the expression for the refractive index of the liquid in terms of x and y.

Draw a ray diagram to show image formation when the concave mirror produces a real, inverted and magnified image of the object.

Explain two advantages of a reflecting telescope over a refracting telescope.

Obtain the mirror formula and write the expression for the linear magnification.

In an optics experiment, with the position of the object fixed, a student varies the position of a convex lens and for each position, the screen is adjusted to get a clear image of the object. A graph between the object distance u and the image distance v, from the lens, is plotted using the same scale for the two axes. A straight line passing through the origin and making an angle of 45^o with the x-axis meets the experimental curve at P. The coordinates of P will be

• (2f, 2f)

• (f/2, f/2)

• (f,f)

• (4f, 4f)

A student measures the focal length of the convex lens by putting an object pin at a distance ‘u’ from the lens and measuring the distance ‘v’ of the image pin. The graph between ‘u’ and ‘v’ plotted by the student should look like

An experiment is performed to find the refractive index of glass using a travelling microscope. In this experiment distance are measured by 

• a vernier scale provided on the microscope

• a standard laboratory scale 

• a meter scale provided on the microscope 

• a screw gauage provided on the microscope

Two lenses of power -15D and +5D are in contact with each other. The focal length of the combination is

• -20 cm

• -10 cm

• +20 cm

• +10 cm