Mist is a
A medium which transmits rays of light so diffused that objects cannot be seen distinctly; that is, the medium is only partially transparent.
Wool is a
Objects through which we cannot see are called opaque objects. A medium that does not allow light to pass through it is called an opaque medium.
Examples of opaque medium are a pencil box, wool, a wooden screen, a book, a towel, a ceramic plate and chart paper.
In order to emit light, the object must have its own source of energy. A torch shines because of the chemical energy stored in its batteries, whereas all stars shine using energy created by nuclear fusion. Sun also emits light as a result of fusion of Hydrogen atoms. Hence they are considered as Luminous objects.
Moons and planets
The most reflected body/ moon in our solar system is Enceladus, a moon of Saturn. It reflects about 90% of light that falls on its surface.
Vacuum is a
A medium which has the property of transmitting rays of light in such a way that the human eye may see through the medium distinctly is called transparent medium. As vacuum consists of nothing so light can easily pass through it without being absorbed or reflected . Hence we can also say vacuum is the best and 100% transparent medium.
Rectilinear propagation of light means
The rectilinear propagation of light means that light travels in straight lines as a wave. In a pinhole camera, the light rays reflecting from the bottom of the object travel in a straight line through the pinhole to the film.
A non luminous body can be made luminous by
A non luminous object can be made luminous by heating it. Take an iron rod & heat it on a gas flame. In about two minutes, the iron wire will get red hot & start emitting light.
The speed of light is
The speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second), and in theory nothing can travel faster than light.
The light from the sun reaches the earth in
Sunlight travels at the speed of light. Photons emitted from the surface of the Sun need to travel across the vacuum of space to reach our eyes. The short answer is that it takes sunlight an average of 8 minutes and 20 seconds to travel from the Sun to the Earth.
A body which emits light by itself is
Objects that emit light on their own is called as luminous body.
Sun is the best example
The star which is very bright during early evening
The evening star is not a star but the planet Venus, when it is near greatest eastern elongation. This means it is as far east of the sun as possible, so that at sunset, it is the brightest object in the sky and can be easily seen in the deepening twilight.
The size of a shadow of an opaque object close to the screen and away from the source of light
The size of the shadow of an opaque object close to the screen and away from the source of light decreases.
This takes place from smooth polished surface when a beam of light falls on it
The process through which light rays falling on the surface on an object are sent back is called reflection of light. Thus, when light falls on the surface of an object it sends back the light. The objects having shiny or polished surface reflects more light compared to the objects having dull or unpolished surface.
The image formed in pinhole camera is
The image produced by a pinhole camera is usually smaller than the object and appears to be inverted on both the vertical and horizontal axis when compared to the actual object.
An optical medium having uniform composition throughout is
A homogeneous medium has uniform properties throughout its volume. That is it does not have lumps of different stuff in it.
A dark patch formed by an opaque body placed in the path of light is called
An opaque object blocking the path of light is called a shadow. A shadow is a dark region, and is formed only when a light source, an opaque object and a screen are present. Opaque objects form shadows because light is not able to bend around them.Shadows are seen more clearly on light screens.
Reflection does not takes place from a
Reflection takes place whenever ray of light travels from a transparent medium towards an opaque medium (shown in the figure below). The opaque medium does not let the light pass through.
The shadow is the dark outline of
A shadow is a dark outline or image cast by an opaque object that blocks light coming from a source of light. It is formed when light hits the opaque object which does not let the light pass through it.
Shadows are formed only when the
This screen is a must to receive the shadow
Luminous objects are objects
The smooth polished surface from which reflection takes place is
A red hot iron wire starts emitting light, at this time the temperature of the iron is
A non luminous object can be made luminous by heating it. Take an iron rod & heat it on a gas flame. In about two minutes, the iron wire will get red hot & start emitting light. At this moment, the temperature of iron is between 600 - 800 degrees Celsius
As light moves towards the object, the shadow becomes larger. As light moves away from the object, the shadow becomes smaller. As light moves closer, the shadow becomes longer and wider.
An example for the rectilinear propagation of light is
Effects of rectilinear propagation of light:
- Formation of shadow
- Formation of day and night
- Formation of image from a pinhole camera