Why don't we have interference when two candles are placed close to each other and the intensity is seen at a distant screen? What happens if the candles are replaced by laser sources?

Why don't we hear sounds when our ears are closed?

Two polaroids are placed 90^(@) to each other and the transmitted intensity is zero. What happens when one more polaroid is placed between these two bisecting the angle between them?

No interference pattern is detected when two coherent sources are infinitely close to each other. Why?

Two wave pulses identical in shape but inverted with respect to each other are produced at the two ends of a stretched string. At an instant when the pulses reach the middle, the string becomes completely straight. What happens to the energy of the two pulses ?

A glass rod rubbed with silk is brought close to two uncharged spheres in contact with each other inducing charges on them as shown in figure. a. What happens when the spheres are slightly separated. b. the glass rod is subsequently removed. c. the spheres are separated far apart.

What is the effect on the interference fringes in a Young' double slit experiment due to each of the following operations. a. the screen is moved away from the plane of the slits. b. the (monolchromatic) source is replaced by another (monochromatic) source of shorter wavelength. c. the separation between the two slits is increased. d. the source slit is moved closer to the double slit plane: e. the width of the source slit is increased. f. The monochromatic source is replaced by a source of white light? (in each operation, take all parameters, other than the one specified, to remain unchanged).

Three identical lamps each having a resistance R are connected to the battery of emf as shown in the figure. Suddenly the switch S is closed. (a) Calculate the current in the circuit when S is open and closed (b) What happens to the intensities of the bulbs A,B and C. (c ) Calculate the voltage across the three bulbs when S is open and closed (d) Calculate the power delivered to the circuit when S is opened and closed (e ) Does the power delivered to the circuit decreases, increases or remain same?

Two coil A & B having 15 turns and 20 turns respectively are placed close to each other. When 4A current is passing through the coil A then flux linked with coil A is 1.6xx10^(-4) weber per turn. If 5A current is passed through coil B, then calculate the flux linked per turn of coil B.

A small candle 2.5 cm height is placed in front of a concave mirror of radius of curvature 36 cm at a distance 27 cm from the concave mirror. i. At what distance from the mirror should a screen be placed in order to receive a sharp image ? ii. Describe the nature and size of the image. iii. If the candle is moved close to the mirror, what will be the position of the screen ?

Two coherent narrow slits emitting sound of wavelength lambda in the same phase are placed parallet to each other at a small separation of 2 lambda . The sound is delected by maving a delector on the screen at a distance D(gt gt lambda) from the slit S_(1) as shows in figure. Find the distance y such that the intensity at P is equal to intensity at O .