Advertisements
Advertisements
प्रश्न
A short pulse of white light is incident from air to a glass slab at normal incidence. After travelling through the slab, the first colour to emerge is ______.
पर्याय
blue
green
violent
red
Advertisements
उत्तर
A short pulse of white light is incident from air to a glass slab at normal incidence. After travelling through the slab, the first colour to emerge is red.
Explanation:
As velocity of wave is given by the relation `v = f λ`. When light ray goes from one medium to other medium, the frequency of light remains unchanged. Hence `v oo λ` or greater the wavelength, greater the speed.
The light of red colour is of the highest wavelength and therefore of the highest speed. Therefore, after travelling through the slab, the red colour emerges first.
APPEARS IN
संबंधित प्रश्न
Give a scientific reason:
Danger signals are red in colour.
Why does unpolarised light from a source show a variation in intensity when viewed through a polaroid which is rotated?
Write two points of difference between the phenomena of interference and diffraction.
What is linearly polarized light?
The image formed by a concave mirror
A convex lens is made of a material having refractive index
\[1 \cdot 2\] Both the surfaces of the lens are convex. If it is dipped into water (μ = 1.33), it will behave like
A point object O is placed on the principal axis of a convex lens of focal length f = 20 cm at a distance of 40 cm to the left of it. The diameter of the lens is 10 cm. An eye is placed 60 cm to right of the lens and a distance h below the principal axis. The maximum value of h to see the image is
A concave mirror having a radius of curvature 40 cm is placed in front of an illuminated point source at a distance of 30 cm from it. Find the location of the image.
A 3 cm tall object is placed at a distance of 7.5 cm from a convex mirror of focal length 6 cm. Find the location, size and nature of the image.
A cylindrical vessel, whose diameter and height both are equal to 30 cm, is placed on a horizontal surface and a small particle P is placed in it at a distance of 5.0 cm from the centre. An eye is placed at a position such that the edge of the bottom is just visible (see figure). The particle P is in the plane of drawing. Up to what minimum height should water be poured in the vessel to make the particle P visible?
Light falls from glass (μ = 1.5) to air. Find the angle of incidence for which the angle of deviation is 90°.
A point source is placed at a depth h below the surface of water (refractive index = μ). (a) Show that light escapes through a circular area on the water surface with its centre directly above the point source. (b) Find the angle subtended by a radius of the area on the source.
A container contains water up to a height of 20 cm and there is a point source at the centre of the bottom of the container. A rubber ring of radius r floats centrally on the water. The ceiling of the room is 2.0 m above the water surface. (a) Find the radius of the shadow of the ring formed on the ceiling if r = 15 cm. (b) Find the maximum value of r for which the shadow of the ring is formed on the ceiling. Refractive index of water = 4/3.
One end of a cylindrical glass rod (μ = 1.5) of radius 1.0 cm is rounded in the shape of a hemisphere. The rod is immersed in water (μ = 4/3) and an object is placed in the water along the axis of the rod at a distance of 8.0 cm from the rounded edge. Locate the image of the object.
A paperweight in the form of a hemisphere of radius 3.0 cm is used to hold down a printed page. An observer looks at the page vertically through the paperweight. At what height above the page will the printed letters near the centre appear to the observer?
Answer the following question in detail.
Explain the formation of a secondary rainbow. For which angular range with the horizontal is it visible?
A plano-convex lens is made of material having refractive index 1.5. The radius of curvature of curved surface is 40 cm. The focal length of the lens is ____________ cm.
