QL State the laws of reflection. (CBSE 2019)
Ans. Laws of Reflection:
) The angle of incldence is equal to the angle of
reflection, and
(ü) The incident ray. the normal to the mirror at the
point of incidenceand the reflected ray, all le in
the same plane.
Q2. List four characteristics of the image fomed by
aconcave mirror of focal length 40 cm when the
object is placed in front of it at a distance of 20 cm
from its pole. (COSE 2019)
Ans.
GTiP
Here, object distance - 20 cm ond focal length = 40
cm, i.e., object is placed between pole and focus of the
Concove mlrror.
Four characteristics of image formed by the glven
concave mirror are:
() Image is virtual
(ü) Image is erect
(ii) Image is enlarged/magnified
(iv) Image is formed behind the mirror.
,Q9. State laws of refraction of light. (CBSE 2019)
Ans. Laws of refraction of light:
() The incident ray. the refracted ray and the normal
to the interface of two transparent media at the
point of incldence. all le in the same plane.
(1) The ratio of sine of angle of incidence to the
slne of angle of refraction Is a constant for the
ight of a given colour and for the given pair of
media. This law is also known as Snell's law of
refraction.
Q10. Define absolute refractive index and express it
mathematically. (CBSE 2019)
Ans. Refractive index of a transparent medium with
respect to vacuum or alr is called absolute refractive
index.
Mathematically.
Absolute refractive index of a medium (u)
Speed of ight in vacuum or air (c)
Speed of ight in the medium (v)
, Q4. Name the type of mirror which facilitates:
() Shaving,
(1) Observing large Images of the teeth of a
patient, and
(ii) Observing the rear view in vehlcles.
Give reason to justify your answer in each case.
(CBSE 2020)
Ans. () Concave mirror facilitates shaving because
when the face is held within the focus of concave
mirror, then an erect and enlarged Image of the
face is seen in it.
() Concave mirrors are used for observing large
Images of the teeth of a patient because they
produce enlarged and erect images.
(il) Convex mirrors are used as rear-view (wing)
mirrors in vehicles because they have a wider
field of view and give an erect inmage.
Ans. Laws of Reflection:
) The angle of incldence is equal to the angle of
reflection, and
(ü) The incident ray. the normal to the mirror at the
point of incidenceand the reflected ray, all le in
the same plane.
Q2. List four characteristics of the image fomed by
aconcave mirror of focal length 40 cm when the
object is placed in front of it at a distance of 20 cm
from its pole. (COSE 2019)
Ans.
GTiP
Here, object distance - 20 cm ond focal length = 40
cm, i.e., object is placed between pole and focus of the
Concove mlrror.
Four characteristics of image formed by the glven
concave mirror are:
() Image is virtual
(ü) Image is erect
(ii) Image is enlarged/magnified
(iv) Image is formed behind the mirror.
,Q9. State laws of refraction of light. (CBSE 2019)
Ans. Laws of refraction of light:
() The incident ray. the refracted ray and the normal
to the interface of two transparent media at the
point of incldence. all le in the same plane.
(1) The ratio of sine of angle of incidence to the
slne of angle of refraction Is a constant for the
ight of a given colour and for the given pair of
media. This law is also known as Snell's law of
refraction.
Q10. Define absolute refractive index and express it
mathematically. (CBSE 2019)
Ans. Refractive index of a transparent medium with
respect to vacuum or alr is called absolute refractive
index.
Mathematically.
Absolute refractive index of a medium (u)
Speed of ight in vacuum or air (c)
Speed of ight in the medium (v)
, Q4. Name the type of mirror which facilitates:
() Shaving,
(1) Observing large Images of the teeth of a
patient, and
(ii) Observing the rear view in vehlcles.
Give reason to justify your answer in each case.
(CBSE 2020)
Ans. () Concave mirror facilitates shaving because
when the face is held within the focus of concave
mirror, then an erect and enlarged Image of the
face is seen in it.
() Concave mirrors are used for observing large
Images of the teeth of a patient because they
produce enlarged and erect images.
(il) Convex mirrors are used as rear-view (wing)
mirrors in vehicles because they have a wider
field of view and give an erect inmage.
