Science (English Medium) Class 12 - CBSE Question Bank Solutions

When are two objects just resolved? Explain.

How can the resolving power of a compound microscope be increased? Use relevant formula to support your answer.

A 10 V cell of negligible internal resistance is connected in parallel across a battery of emf 200 V and internal resistance 38 Ω as shown in the figure. Find the value of current in the circuit.

In a potentiometer arrangement for determining the emf of a cell, the balance point of the cell in open circuit is 350 cm. When a resistance of 9 Ω is used in the external circuit of the cell, the balance point shifts to 300 cm. Determine the internal resistance of the cell.

Does the magnifying power of a microscope depend on the colour of the light used? Justify your answer.

A light bulb and a solenoid are connected in series across an ac source of voltage. Explain, how the glow of the light bulb will be affected when an iron rod is inserted in the solenoid.

The figure shows three infinitely long straight parallel current carrying conductors. Find the

1. magnitude and direction of the net magnetic field at point A lying on conductor 1,
2. magnetic force on conductor 2.

Plot a graph showing variation of voltage vs the current drawn from the cell. How can one get information from this plot about the emf of the cell and its internal resistance?

(i) State the essential conditions for diffraction of light.
(ii) Explain diffraction of light due to a narrow single slit and the formation of pattern of fringes on the screen.
(iii) Find the relation for width of central maximum in terms of wavelength 'λ', width of slit 'a', and separation between slit and screen 'D'.
(iv) If the width of the slit is made double the original width, how does it affect the size and intensity of the central band?

Why cannot two independent monochromatic sources produce sustained interference pattern?
Deduce, with the help of Young's arrangement to produce interference pattern, an expression for the fringe width.

Draw a ray diagram showing image formation in a compound microscope ?

How is 'limit of resolution' related to resolving power of a microscope ?

Suggest two ways by which the resolving power of a microscope can be increased?

A potentiometer wire of length 1.0 m has a resistance of 15 Ω. It is connected to a 5 V battery in series with a resistance of 5 Ω. Determine the emf of the primary cell which gives a balance point at 60 cm.

Two long straight parallel conductors 'a' and 'b', carrying steady currents I_a and I_b are separated by a distance d. Write the magnitude and direction of the magnetic field produced by the conductor 'a' at the points along the conductor 'b'. If the currents are flowing in the same direction, what is the nature and magnitude of the force between the two conductors?

 Two infinitely large plane thin parallel sheets having surface charge densities σ₁ and σ₂ (σ₁ > σ₂) are shown in the figure. Write the magnitudes and directions of the net fields in the regions marked II and III.

A compound microscope has an objective of focal length 1.25 cm and eyepiece of focal length 5 cm. A small object is kept at 2.5 cm from the objective. If the final image formed is at infinity, find the distance between the objective and the eyepiece ?

A cell of emf ‘E’ and internal resistance ‘r’ draws a current ‘I’. Write the relation between terminal voltage ‘V’ in terms of E, I and r ?

Draw a ray diagram showing the image formation by a compound microscope. Hence obtained expression for total magnification when the image is formed at infinity.

Distinguish between myopia and hypermetropia. Show diagrammatically how these defects can be corrected.