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Absolute and Relative Refractive Index

Fill in the b...

Question

Fill in the blanks :

(a) Water is optically _ than air.

(b) Air is optically _ than glass.

(c) When a ray of light travels from water to air, it bends _ the normal.

(d) When a ray of light travels from air to glass, it bends _ the normal.

(e) When white light passes through a prism, it _

(f) The splitting of white light into its constituent colours is called _

(g) A _ mirror is obtained on silvering the outer surface of a part of a hollow glass sphere.

(h) Radius of curvature of a spherical mirror is _ its focal length.

(i) The angle of incidence for a ray of light passing through the centre of curvature of aspherical mirror is _

(j) A _ mirror always forms a virtual image.

(k) A concave mirror forms a virtual image for an object placed ___

Ans. (a) denser (b) rarer (c) away from (d) towards (e) disperses (f) dispersion

(g) concave (h) two times (i) $0^{\circ}$ (j) convex (k) between pole and focus

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Solution

(a) Water is opitcally denser than air.
(b) Air is optically rarer than glass.
(c) When a ray of light travels from water to air, it bends away from the normal.
(d) When a ray of light travels from air to glass, it bends towards the normal.
(e) When white light passes through a prism, it disperses
(f) The splitting of white light into its constituent colours is called dispersion.
(g) A concave mirror is obtained on silvering the outer surface of a part of a hollow glass sphere.
(h) Radius of curvature of a spherical mirror is two times its focal length.
(i) The angle of incidence for a ray of light passing through the centre of curvature of a spherical mirror is 0°
(j) A convex mirror always forms a virtual image.
(k) A concave mirror forms a virtual image for an object placed between pole and focus.

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Similar questions

Write True or false for each statement :

(a) Water is optically denser than glass.

(b) A ray of light when passes from glass to air, bends towards the normal.

(d) The depth of a pond when seen from above appears to be less.

(e) Light travels at a lower speed in water than in air.

(f) Light travels in the same straight line path while passing through different media.

(g) The angle formed between the normal and the refracted ray is known as the angle of incidence.

(h) At the point of incidence, a line drawn at right angles to the surface, separating the two media, is called the normal.

(i) Image is formed by a mirror due to refraction of light.

(j) Rays of light incident parallel to the principal axis pass through the focus after reflection from a concave mirror.

(k) A convex mirror is used as a shaving mirror.

(l) The focal length of a convex mirror is equal to its adius of curvature.

(m) A concave mirror converges the light rays, but a convex mirror diverges them.

(n) A virtual image formed by a spherical mirror is always erect and situated behind the mirror.

Ans. True - (d), (e), (h), (j), (m), (n),

False - (a), (b), (c), (f), (g), (i), (k), (l)

Light travels more quickly through water than through glass. (a) Which is optically denser : water or glass ? (b) If a ray of light passes from glass into water, which way will it bend : towards the normal or away from the normal ?

Q. State whether the following statements are true or false. Rewrite the false statements correctly.
(a) The laws of reflection hold good only for plane mirrors and not for spherical mirrors.
(b) The radius of curvature is double the focal length of a concave mirror.
(c) A ray passing through the focus cuts through the principal axis of a concave mirror after reflection.
(d) When an object is placed between a concave mirror and its focus, the image formed is virtual, erect and larger than the object.
(e) The image formed on a cinema screen is virtual.
(f) A convex mirror is used by stage artists.
(g) A convex mirror always gives real images.
(h) A pinhole camera gives a real image.
(i) A convex surface bulges inwards.
(j) Incident rays parallel to the principal axis of a curved mirror pass through the focus after reflection.
(k) A concave mirror always forms a real image.
(l) There can be many reflected rays for a single incident ray falling on a reflecting surface.

Select the correct alternative :

(a) The speed of light in air or vacuum is :

(i) $3 \times 10^{8} m s - 1$

(ii $2.25 \times 10^{8} m s^{- 1}$

(iii) $3.32 m s^{- 1}$

(iv) $2.0 \times 10^{8} m s^{- 1}$

(b) A ray of light moving from an optically rarer to a denser medium :

(i) bends away from the normal

(ii) bends towards the normal

(iii) remains undeviated

(iv) none of the above.

(i) angle of deviation

(ii) angle of incidence

(iii) angle of refraction

(iv) angle of emergence.

(d) The property of splitting of white light into its seven constituent colours is known as :

(i) rectilinear propagation

(ii) refraction

(iii) reflection

(iv) dispersion.

(e) The seven colours in the spectrum of sunlight in order, are represented as :

(i) VIBGYOR (ii) VIGYBOR

(iii) BIVGYOR (iv) RYOBIVG

(f) A ray of light passing through centre of curvature of a spherical mirror, after reflection :

(i) passes through the focus

(ii) passes through the pole

(iii) becomes parallel to the principal axis

(iv) retraces its own path.

(g) If the radius of curvature of a concave mirror is 20 cm, its focal length is :

(i) 10 cm (ii) 20 cm

(iii) 40 cm (iv) 80 cm.

(h) The image formed by a convex mirror ix :

(i) erect and diminished

(ii) erect and enlarged

(iii) inverted and diminished

(iv) inverted and enlarged.

(i) The image formed by a concave mirror is of the same size as the object, if the object is placed :

(i) at the focus

(ii) between the pole and focus

(iii) between the focus and centre of curvature

(iv) at the centre of curvature.

(j) A convex mirror is used :

(i) as a shaving mirror

(ii) as a head mirror by a dentist

(iii) as a rear view mirror by a driver

(iv) as a reflector in torch.

Ans. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv), (e)-(i), (f)-(iv), (g)-(i), (h)-(i), (i)-(iv), (j)-(iii)

Q. What is the angle of incidence when a ray of light incident on a concave mirror from its centre of curvature?

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