Q19. Distinguish between concave mirror and convex mirror.
||Reflection takes place at the concave surface (bent in surface).
||Reflection takes place at the convex surface (bulging out surface).
||A parallel beam of light falling on this mirror converges at a point after reflection.
||A parallel beam of light falling on this mirror appears to diverge from a point after reflection.
||It is a converging mirror.
||It is a diverging mirror.
||It has a real focus which lies in the front of the mirror.
||It has a virtual Focus which lies behind the mirror.
Q2. What are metals?
Ans. Metals are malleable, ductile and good conductor of heat and electricity. They possess high melting point and boiling point. Example: Copper, Sodium, Aluminum, Potassium etc.
On the basis of chemical reaction, metals are defined as follows:
Metals are those elements which form positive ions( cations) by losing electrons. Because of this property metals are also known as electropositive elements.
Q36. Explain why a ray of light passing through the center of curvature of a concave mirror gets reflected along the same path.
Ans. This is because the angle of incidence is 0o, that is the rays passing through the center of curvature is incident it normally to the mirror.
Q35. Can a plane mirror called as spherical mirror?
Ans. Yes, a plane mirror can be called a spherical mirror of infinite radius.
Q34. When light falls on the surface of an object, what will happen?
Ans. It may be
Q33. Name one means of communication provided by light.
Ans. Optical Fiber, which transmits many telephone messages at the same time.
Q32. Name the type of mirrors used in the following situations:
- Headlight of a car,
- Side view mirror of a vehicle,
- Solar furnace.
Support your answer with reason.
- Headlight of a car: Concave Mirrors are used in vehicles headlights to get powerful beams of light. This is because when a lighted bulb is placed at the focus of a concave reflector, then it produces a powerful beam of parallel light rays. This helps us to see things up to a considerable distance in the darkness of night.
- Side view mirror of a vehicle: It is used as rear view Mirror in vehicles to see the traffic at the rare side. (Convex Mirrors are preferred because there always give an erect even though diminished image, they have a wider field of view as they are curved outwards).
- Solar furnace: Large Concave Mirrors are used in the Solar furnace to concentrate sun light to produce maximum heat. Solar furnace is placed at the focus of a large concave reflector. It focuses the sun’s heat rays on the furnace due to which the Solar furnace gets very hot.
Q31. The magnification produced by a plane mirror is +1. What does it mean?
Ans. The value 1 shows that, size of the image formed by the plane mirror is equal to the object.
The positive sign(+) in the value shows that the image formed by the plane mirror is virtual and erect.
Q30. Define magnification.
Ans. Magnification is the ratio of height of the image to the height of the object. It is the relative extent to which the image of an object is magnified with respect to the object.
Magnification of real image is negative.
Magnification of virtual image is positive.
Q29. What is mirror formula?
Ans. The relationship between object distance( distance of the object from the pole of the mirror ‘u’), image distance( distance of the image from the pole of the mirror ‘v’) and focal length(f) is known as mirror formula which is expressed as
l/v + l/u = l/f