NCERT Solutions for Class 10 Science Chapter 10
Light Reflection and Refraction
Questions Page: 168
1. Define the principal focus of a concave mirror.
Answer-
Light rays that are parallel to the principal axis of a concave mirror converge at a specific point on its principal axis
after reflecting from the mirror. This point is called the principal focus of the concave mirror.
2. The radius of curvature of a spherical mirror is 20 cm. What is its focal length?
Answer-
Radius of curvature (R) = 20 cm
Radius of curvature of the spherical mirror = 2 × Focal length (f)
R = 2f
f= R/2 = = 10
Therefore, the focal length of the spherical mirror is 10 cm.
3. Name the mirror that can give an erect and enlarged image of an object.
Answer-
The mirror that can give an erect and enlarged image of an object is a Concave Mirror.
4. Why do we prefer a convex mirror as a rear-view mirror in vehicles?
Answer-
A convex mirror is preferred as a rear-view mirror in cars and vehicles as it gives a wider field of view, which helps the
driver see most of the traffic behind him. Convex mirrors always form an erect, virtual, and diminished image of the
objects placed in front of it.
, NCERT Solutions for Class 10 Science Chapter 10
Light Reflection and Refraction
Questions Page No: 171
1. Find the focal length of a convex mirror whose radius of curvature is 32 cm.
Answer-
Radius of curvature (R) = 32 cm
Radius of curvature = 2 × Focal length (f)
R= 2f
f = R/2 = 32/2 = 16
Therefore, the focal length of the given convex mirror is 16 cm.
2. A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front
of it. Where is the image located?
Answer-
Magnification produced by a spherical mirror:
Object distance (u) = – 10 cm
v = 3 × (- 10) = – 30 cm
Therefore, the negative sign indicates that an inverted image is formed in front of the given concave mirror at a
distance of 30 cm.
Light Reflection and Refraction
Questions Page: 168
1. Define the principal focus of a concave mirror.
Answer-
Light rays that are parallel to the principal axis of a concave mirror converge at a specific point on its principal axis
after reflecting from the mirror. This point is called the principal focus of the concave mirror.
2. The radius of curvature of a spherical mirror is 20 cm. What is its focal length?
Answer-
Radius of curvature (R) = 20 cm
Radius of curvature of the spherical mirror = 2 × Focal length (f)
R = 2f
f= R/2 = = 10
Therefore, the focal length of the spherical mirror is 10 cm.
3. Name the mirror that can give an erect and enlarged image of an object.
Answer-
The mirror that can give an erect and enlarged image of an object is a Concave Mirror.
4. Why do we prefer a convex mirror as a rear-view mirror in vehicles?
Answer-
A convex mirror is preferred as a rear-view mirror in cars and vehicles as it gives a wider field of view, which helps the
driver see most of the traffic behind him. Convex mirrors always form an erect, virtual, and diminished image of the
objects placed in front of it.
, NCERT Solutions for Class 10 Science Chapter 10
Light Reflection and Refraction
Questions Page No: 171
1. Find the focal length of a convex mirror whose radius of curvature is 32 cm.
Answer-
Radius of curvature (R) = 32 cm
Radius of curvature = 2 × Focal length (f)
R= 2f
f = R/2 = 32/2 = 16
Therefore, the focal length of the given convex mirror is 16 cm.
2. A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front
of it. Where is the image located?
Answer-
Magnification produced by a spherical mirror:
Object distance (u) = – 10 cm
v = 3 × (- 10) = – 30 cm
Therefore, the negative sign indicates that an inverted image is formed in front of the given concave mirror at a
distance of 30 cm.
