1. What is the focal length of a plane mirror?
2. What is the magnification of a plane mirror?
3. What is meant by the power of a lens?
4. What is one dioptre?
5. We know that plane and convex mirrors produce virtual images of objects. Can they produce real images under some circumstances? Explain. [5 MARKS]
1. What is the focal length of a plane mirror?
2. What is the magnification of a plane mirror?
3. What is meant by the power of a lens?
4. What is one dioptre?
5. We know that plane and convex mirrors produce virtual images of objects. Can they produce real images under some circumstances? Explain. [5 MARKS]
Each point: 1 Mark
1. Mathematically, a plane mirror can be considered to be the limit of either a concave or a convex spherical curved mirror as the radius, and therefore, the focal length becomes infinite.
2. A plane mirror forms a virtual and erect image of size same as that of the object.
Image height = object height
m=hiho=1
m = 1
3. The power of a lens is the reciprocal of its focal length.
4. One dioptre is the power of the lens whose focal length is 1 m.
5. Rays converging to a point ‘behind’ a plane or convex mirror are reflected at the point in front of the mirror on the screen. In other words, a plane or convex mirror can produce a real image but only if the object is virtual.
Each point: 1 Mark
1. Mathematically, a plane mirror can be considered to be the limit of either a concave or a convex spherical curved mirror as the radius, and therefore, the focal length becomes infinite.
2. A plane mirror forms a virtual and erect image of size same as that of the object.
Image height = object height
m=hiho=1
m = 1
3. The power of a lens is the reciprocal of its focal length.
4. One dioptre is the power of the lens whose focal length is 1 m.
5. Rays converging to a point ‘behind’ a plane or convex mirror are reflected at the point in front of the mirror on the screen. In other words, a plane or convex mirror can produce a real image but only if the object is virtual.
