Definition
Virtual and Real images
| Real Image | Virtual Image |
| Real image can be seen on the screen. | Virtual images cannot be formed on the screen. |
| It is always inverted | It is always erect. |
| It is formed when ray of light after reflection.refraction meet at some point | It is formed when ray of light appear to meet at a point. |
| It is formed due to actual intersection of light ray. | It is formed due to imaginary intersection of light ray. |
Shortcut
Difference between real and virtual images formed by spherical mirrors
- A real image is defined as one that is formed when rays of light are directed in a fixed point. A real image can be projected or seen on a screen. The best example of a real image is the one formed on a cinema screen.
- A virtual image is defined as the opposite of a real image, therefore an image that cannot be obtained on a screen is referred to as a virtual image. The explanation for this is the fact that the rays of light that form a virtual image never converge therefore a virtual image can never be projected onto a screen. The best example of a virtual image is your reflection in the mirror.
- Real images are produced by intersecting rays while virtual images are produced by diverging rays.
- Real images can be projected on a screen while virtual ones cannot.
- Real images are formed by two opposite lens, concave and convex.
- Virtual images are always upright while real images are always inverted.
Definition
Real and virtual image
Real image is formed by the actual intersection of light rays. It can be obtained on a screen. Hence, projectors form real images.
Virtual image is formed when the light rays appear to be originating from a point but does not actually meet. It can be seen by human eyes. Hence, rear-view mirrors form virtual images.
Virtual image is formed when the light rays appear to be originating from a point but does not actually meet. It can be seen by human eyes. Hence, rear-view mirrors form virtual images.
Example
Laws of reflection
In the diagram, the ray of light approaching the mirror is known as the incident ray. The ray of light that leaves the mirror is known as the reflected ray. At the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror. This line is known as a normal line.
The normal line divides the angle between the incident ray and the reflected ray into two equal angles. The angle between the incident ray and the normal is known as the angle of incidence. The angle between the reflected ray and the normal is known as the angle of reflection. The laws of reflection are as follows:
The normal line divides the angle between the incident ray and the reflected ray into two equal angles. The angle between the incident ray and the normal is known as the angle of incidence. The angle between the reflected ray and the normal is known as the angle of reflection. The laws of reflection are as follows:
- The incident ray, the reflected ray and the normal to the reflection surface at the point of the incidence lie in the same plane.
- The angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal.
- The reflected ray and the incident ray are on the opposite sides of the normal.
Definition
Image Formation from Spherical Reflecting Surfaces
The curved shining surface of a spoon acts as a mirror. The inner surface of a spoon acts like a concave mirror, while its outer surface acts like a convex mirror.Hence the inner surface of spoon shows inverted image and outer shows erect.
Diagram
Reflection of rays from a spherical mirror
Rays incident on a spherical mirror exhibits the following behaviour:
- Light ray passing through (or directed towards) the center of curvature retraces its path after reflection.
- Light ray parallel to the principal axis passes through (or appears to diverge from) focus after reflection.
- Light ray passing through (or directed towards) focus is reflected as a ray parallel to the principal axis.
- Light ray incident on the pole of the mirror is reflected at an angle of reflection (with principal axis) equal to the angle of incidence (with principal axis).
Diagram
Images formed by convex mirrors for object placed at different distances
A convex mirror bulges outwards. When parallel rays of light strike the mirror, they are reflected so that they spread out or diverge. For this reason a convex mirror is also known as a diverging mirror. If these reflected rays are extended behind the mirror by dotted lines, they are seen to meet at a point. This point is the focus of the convex mirror. It forms small, upright, virtual images.
Diagram
Images formed by concave mirrors for object placed at different distances
A concave mirror curves inwards. When parallel rays of light strike the mirror, they are reflected so that they converge to a point. For this reason a concave mirror is also known as a converging mirror. This converging point is the focus of the concave mirror.
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