Assertion:  The clouds in sky generally appear to be whitish. 

Reason:  Diffraction due to clouds is efficient in equal measure at all wavelengths.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Sodium lamps are used in foggy conditions because

• yellow light is scattered less by the fog particles

• yellow light is scattered more by the fog particles

• yellow light is unaffected during its passage through the fog

• wavelength of yellow light is the mean of the visible one 

A monochromatic beam of light is used for the formation of fringes on the screen by illuminating the two slits in the Young's double slit interference experiment. When a thin film of mica is interposed in the path of one of the interfering beams then

• the fringe width increases

• the fringe width decreases

• the fringe width remains the same but the pattern shifts

• the fringe pattern disappears

When a compact disc is illuminated by a source of white light, coloured lines are observed. This is due to

• dispersion

• diffraction

• interference

• refraction

Assertion: At the first glance, the top surface of the Morpho butterfly's wing appears a beautiful blue-green. If the wing moves the colour changes.

Reason: Different pigments in the wing reflect light at different angles.

• If both assertion and reason are true and reason is correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion 

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion: A famous painting was painted by not using brush strokes in the usual manner, but rather a myriad of small colour dots. In this painting the colour you see at any given place on the painting changes as you move away.

Reason: The angular separation of adjacent dots changes with the distance from the painting.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion:  Crystalline solids can cause X-rays to diffract. 

Reason:  Interatomic distance in crystalline solids is of the order of 0.1 nm.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If  both assertion and reason are false

178.

When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if the light is

• polarised

• of longer wavelength

• of shorter wavelength

• of high intensity

A double slit experiment is performed with light of wavelength  500 nm. A thin film of thickness 2 μm and refractive index 1.5 is introduced in the path of the upper beam. The location of central maximum will

• remain unshifted

• shift downward by nearly two fringes

• shift upward by nearly two fringes

• shift downward by 10 fringes

Assertion:  The stars twinkle while the planets do not. 

Reason: The stars are much bigger in size than the planets.

• if both assertion and reason are true and the reason is the correct explanation of the assertion

• if both assertion and reason are true and the reason is not the correct explanation of the assertion

• if assertion is true but reason is false

• if both assertion and reason are false statements