Q1 : In which type of lens linear magnification is always
less then one?
Answer: Concave Lens always has linear magnification
less than one, because it always gives diminished
images.
Q2 : John obtained a magnification of 1 with concave
mirror of focal length 10cm. What is the object distance
from mirror?
Answer: m = 1. Therefore u = v. Apply it in mirror
formula, you will get v = 20 cm.
Q3 : Which mirror has a wider field of view?
Answer: convex mirrors have wilder field view, that's
why these are used as rear view-mirrors in vehicles.
Q4 : Which is optically denser out of the two mediums
M1 and M2 having n = 1.71 and 1.36
respectively.
Answer: M1 (it has higher value of refractive index).
Q5: Identify a mirror having focal length –15cm
Answer: concave mirror (see -ve sign of focal length).
Q6 : Why does a ray change its path when it passes from
one medium to another medium?
Answer: Because of refractive property of light.
Q7 : When a ray of light entering from air is incident on
the surface of a glass slab at an angle
of 90°, what will be the measure of angle of refraction?
Answer: It will be zero degree.
Q8 : Due to which property of light, sharp shadows of
opaque objects are obtained?
Answer: Since light travels in straight lines, any obstacle
obstructing the path will cast its shadow.
Q9 : Two medium with refractive index 1.31 and 1.50
are given. In which case
(i) Bending of light is more (ii)
speed of light is more
Answer: (i) 1.50 and ii) 1.31
Q10 : Why does the coin placed at the bottom of a
container appears to be raised when the
container is filled slowly with water?
Answer: Light ray emerging from water medium to air
medium bends away and then reaches the eye.
Q11: Under what circumstances there won’t be any
refraction of light when it enters from one
medium to another?
Answer: There are two possible cases:
(i) When light incidents at 90 degress (normal) it will
not bend.
(ii) Only applicable when light passes from optical
denser medium to rarer medium, if it is incident at an
angle greater than critical angle, it will reflect (called
internal reflection) but not refract.
Q12 : Can a plane mirror ever form a real image?
Answer: Real image can only be formed when the
reflected rays converge. As such for plane mirrors it is
not possible. However, if the reflected yas are
converged (or appears converged), it can form real
image. Consider a source of light is at infinity (say sun),
and plane mirror is very small in size, its reflected image
will show a circular bright spot (image of the sun) on
the screen.
Q13 : What feature of light corresponds (analogous) to
loudness of sound?
Answer: Brightness
Q14 Identify types of mirror without touching.
Answer: Move mirror to and fro.
Plane Mirror: Mirror image is of true size.
Concave Mirror: Image is curved. Bringing the mirror
closer, magnifies the image. Moving it away, image is
inverted and reduced.
Convex Mirror: Mirror image is always diminished but
erect. The viewpoint is wider.
Q15: What is the focal length of a plane mirror?
Answer: Infinity
Q16: Will the reflected rays converge at point when
a parallel beam of light is incident on a concave
mirror?
Answer: Yes it will converge at the focal point of
concave mirror.
Q17: Name any use of Concave lens.
Answer: Concave lens are mainly used in spectacles for
the correction of shortsightedness.
Q19: Name the type of mirror which always forms
virtual and diminished image.
Answer: convex mirror.
Q20: What is the angle of reflection if a ray falls
normally on a plane mirror?
Answer: Zero
Q21: A ray of light travelling in air enters obliquely
into water. Does the light ray bend towards the
normal or away from the normal. Why?
Answer: When a ray of light travelling in air enters
obliquely into water, it bends towards the normal. It
happens because water is optically denser than air.
Speed of light will also decrease.
Q22: What are the uses of convex mirror?
Answer:
rear-view mirror
reflector of street light
shopping malls and buildings have long paths have
convex mirrors around the corner
Q23: List the uses of concave mirror?
Answer:
shaving mirror
reflector in automobile lights and torches
by dentists to see back side of tooth
reflector of solar furnaces
Q24: How many images are formed for a point
source kept in between two plane mirrors M1 and
M2 at right angles to each other?
Answer: Three.
Q25: What shall be the direction of the incident ray
which after reflection from a spherical mirror
retraces its path?
Answer: In this case incident ray is directed towards the
centre of curvature.
Q26: What are the characteristics of the image
formed on a plane mirror?
Answer: Characteristics of Image formed on plane
mirror are:
1. Image is upright and is of same size as the object.
2. It is virtual
3. Laterally inverted
less then one?
Answer: Concave Lens always has linear magnification
less than one, because it always gives diminished
images.
Q2 : John obtained a magnification of 1 with concave
mirror of focal length 10cm. What is the object distance
from mirror?
Answer: m = 1. Therefore u = v. Apply it in mirror
formula, you will get v = 20 cm.
Q3 : Which mirror has a wider field of view?
Answer: convex mirrors have wilder field view, that's
why these are used as rear view-mirrors in vehicles.
Q4 : Which is optically denser out of the two mediums
M1 and M2 having n = 1.71 and 1.36
respectively.
Answer: M1 (it has higher value of refractive index).
Q5: Identify a mirror having focal length –15cm
Answer: concave mirror (see -ve sign of focal length).
Q6 : Why does a ray change its path when it passes from
one medium to another medium?
Answer: Because of refractive property of light.
Q7 : When a ray of light entering from air is incident on
the surface of a glass slab at an angle
of 90°, what will be the measure of angle of refraction?
Answer: It will be zero degree.
Q8 : Due to which property of light, sharp shadows of
opaque objects are obtained?
Answer: Since light travels in straight lines, any obstacle
obstructing the path will cast its shadow.
Q9 : Two medium with refractive index 1.31 and 1.50
are given. In which case
(i) Bending of light is more (ii)
speed of light is more
Answer: (i) 1.50 and ii) 1.31
Q10 : Why does the coin placed at the bottom of a
container appears to be raised when the
container is filled slowly with water?
Answer: Light ray emerging from water medium to air
medium bends away and then reaches the eye.
Q11: Under what circumstances there won’t be any
refraction of light when it enters from one
medium to another?
Answer: There are two possible cases:
(i) When light incidents at 90 degress (normal) it will
not bend.
(ii) Only applicable when light passes from optical
denser medium to rarer medium, if it is incident at an
angle greater than critical angle, it will reflect (called
internal reflection) but not refract.
Q12 : Can a plane mirror ever form a real image?
Answer: Real image can only be formed when the
reflected rays converge. As such for plane mirrors it is
not possible. However, if the reflected yas are
converged (or appears converged), it can form real
image. Consider a source of light is at infinity (say sun),
and plane mirror is very small in size, its reflected image
will show a circular bright spot (image of the sun) on
the screen.
Q13 : What feature of light corresponds (analogous) to
loudness of sound?
Answer: Brightness
Q14 Identify types of mirror without touching.
Answer: Move mirror to and fro.
Plane Mirror: Mirror image is of true size.
Concave Mirror: Image is curved. Bringing the mirror
closer, magnifies the image. Moving it away, image is
inverted and reduced.
Convex Mirror: Mirror image is always diminished but
erect. The viewpoint is wider.
Q15: What is the focal length of a plane mirror?
Answer: Infinity
Q16: Will the reflected rays converge at point when
a parallel beam of light is incident on a concave
mirror?
Answer: Yes it will converge at the focal point of
concave mirror.
Q17: Name any use of Concave lens.
Answer: Concave lens are mainly used in spectacles for
the correction of shortsightedness.
Q19: Name the type of mirror which always forms
virtual and diminished image.
Answer: convex mirror.
Q20: What is the angle of reflection if a ray falls
normally on a plane mirror?
Answer: Zero
Q21: A ray of light travelling in air enters obliquely
into water. Does the light ray bend towards the
normal or away from the normal. Why?
Answer: When a ray of light travelling in air enters
obliquely into water, it bends towards the normal. It
happens because water is optically denser than air.
Speed of light will also decrease.
Q22: What are the uses of convex mirror?
Answer:
rear-view mirror
reflector of street light
shopping malls and buildings have long paths have
convex mirrors around the corner
Q23: List the uses of concave mirror?
Answer:
shaving mirror
reflector in automobile lights and torches
by dentists to see back side of tooth
reflector of solar furnaces
Q24: How many images are formed for a point
source kept in between two plane mirrors M1 and
M2 at right angles to each other?
Answer: Three.
Q25: What shall be the direction of the incident ray
which after reflection from a spherical mirror
retraces its path?
Answer: In this case incident ray is directed towards the
centre of curvature.
Q26: What are the characteristics of the image
formed on a plane mirror?
Answer: Characteristics of Image formed on plane
mirror are:
1. Image is upright and is of same size as the object.
2. It is virtual
3. Laterally inverted
