PHYSICS [2 Mark Question Answer]

The principal focus of a spherical mirror may be defined as a point on its principal axis where a beam of light parallel to the principal axis converges to or appears to diverge from after reflection from the spherical mirror.

When an object is brought towards the concave mirror, the position of the image moves away from the mirror, and the size increases and it remains inverted but at object position between F and P, the image is virtual, magnified, and erect.

Linear magnification is defined as the ratio of the height of the image to the height of the object. It is taken to be positive for an image to be virtual and erect and negative when the image is real and inverted.
Magnification = height of image / height of object.

A concave mirror forms an enlarged virtual image when the object is kept between focus, F and pole, P

A concave mirror forms a real image equal in size to the object when the object is kept at centre of curvature, C

Two sources of light are
(a). Natural, for e.g. Sun
(b). Artificial, for e.g. Light bulb.

Two characteristics of the image formed by a plane mirror are
(a). The image is erect and virtual
(b). Image and object are of the same size.

The angle of incidence = angle of reflection = 0° because the image is perpendicular to the surface of the plane mirror.

Laws of reflection:

1. The incident ray, the reflected ray, and the normal ray at the point of incidence lie in the same plane.
2. The angle of incidence i is equal to the angle of reflection r i.e. ∠i = ∠r.

Reflection obeys the following two laws
(a). The incident ray, the reflected ray, and the normal at the point of incidence, all lie in the same plane.
(b). The angle of incidence and the angle of reflection are always equal.

Two observations that prove that light travels in a straight line are:-
(a). Sunlight coming through a hole in a dark room, we can easily see that light travels in a straight line
(b). The light coming from laser light, used for presentation, can also be seen to travel in a straight line.

Height of object = 5 cm.
Distance of object = 30 cm.
Focal length of mirror = 40 cm.

Image is virtual, erect, and magnified.

Focal length o f concave mirror= 10 cm. Object distance = 30 cm.

The image is real, inverted, and diminished.

In the case of a convex mirror, all rays incident parallel to the principal axis appears to diverge from a Focal point. So it has a wider field of view as it converges all rays to a single point.

The image formed is virtual, Diminished, and erect.

The position of the image is exactly below the position of the object as in the figure.

Completed path of the incident ray in the following case is:

Completed path of the incident ray in the following case is:

Completed path of the incident ray in the following case is:

When two mirrors are held parallel to each other than, infinite numbers of images are formed and the first two images are shown in this figure.

When two mirrors are held perpendicular then the number of images is 3 according to rule Number of images = 360/X - 1 if 360/X is even Number of images is 360/90 -1 = 4-1 = 3 images.

Normal to the surface of a mirror at any point is the straight line at the right angle to the tangent drawn at that point.

The focus of a concave mirror is a point on the principal axis of the mirror, where all the rays travelling parallel to the principal axis and close to it after reflection from the mirror converge to that point.

Principal focus of a spherical mirror is a point on the principal axis of the mirror, where all the rays travelling parallel to the principal axis and close to it after reflection from the mirror, converge to or appear to diverge from.

The image observed by the eye after reflection from a plane mirror can be completed as follows:

The image observed by the eye after reflection from a plane mirror can be completed as follows:

When the Paper is held perpendicular to the mirror.

When the paper is help parallel to the mirror.

The image formed by a plane mirror is erect and virtual. It is a laterally inverted image. The image formed is of the same size as that of the object. Also, the image and the object are equidistant from the mirror.

Two planes when putting in this way then they will turn the incident ray by 180°.

We can see the reflection of our face on a polished tabletop because a regular reflection occurs in case of a polished surface while on an unpolished tabletop irregular reflection occurs which makes the image of our face unclear.

Two uses of convex mirror are:
(a) It is used as a rear view mirror in automobile to see the traffic behind.
(b) It is used as reflector for street light bulbs.

Reflection obeys the following two laws
(a). The incident ray, the reflected ray, and the normal at the point of incidence, all lie in the same plane.
(b). The angle of incidence and the angle of reflection are always equal.

Linear magnification is defined as the ratio of the height of the image to the height of the object. It is taken to be positive for an image to be virtual and erect and negative when the image is real and inverted.
Magnification = height of image / height of object.

Mirror formula is the relation between the focal length f of the mirror, the distance u of the object from the pole of the mirror, and the distance v of the image from the pole.
Mirror formula is
1/v +1/u = 1/f.

(i) The distance from the pole in the direction of incident ray is taken positive.
(ii) The distance from the pole in the direction opposite to the incident ray is taken negative.

(i) When position of object is at infinity, concave mirror forms a point and Real image at Focus point.
(ii) When position of object is beyond C, concave mirror forms a Diminished, Real and inverted image between F and C.
(iii)When position of object is at C, concave mirror forms a Magnified, Real and inverted image at C.