Short answer questions
D. Answer in brief.
2.
3.
1. What is a source of light?
How do you see non-luminous objects?
How are shadows produced?
4. State the position of the Sun, Moon and
Earth during: (i) a solar eclipse (ii) a lunar
eclipse.
From which portion on the Earth can a total
solar eclipse be seen?
6. What kind of image is formed by a pinhole
camera?
5.
7. On what principle does the action of a
pinhole camera depend?
8. How does a change in the distance of the
object from a pinhole camera affect the size
of the image?
9. What happens when a ray of light falls on a
plane mirror?
Answers
Answer:
4.5litre sample of gas at 20degree celsius is heated to a temperature of 80 degree celsius .if the amount of gas and the pressure of the gas remain constant, what will be the new volume of the gas?
Answer:
What is a source of light?
A light source is anything that makes light. There are natural and artificial light sources. A few examples of natural light sources include the Sun, stars and candles. A few examples of artificial light sources include light bulbs, lamp posts and televisions.
How are non luminous objects visible to eye?
- Non-luminous objects give away light.
- Non-luminous objects reflect the light falling on them.
- Non-luminous objects disperse the light falling on them.
- None of the above.
How are shadows produced?
Shadows are made by blocking light. Light rays travel from a source in straight lines. If an opaque (solid) object gets in the way, it stops light rays from traveling through it. The size and shape of a shadow depend on the position and size of the light source compared to the object.
State the position of the Sun, Moon and Earth during: (i) a solar eclipse (ii) a lunar eclipse.
When the Moon passes between Sun and Earth, the lunar shadow is seen as a solar eclipse on Earth. When Earth passes directly between Sun and Moon, its shadow creates a lunar eclipse.
Lunar eclipses can only happen when the Moon is opposite the Sun in the sky, a monthly occurrence we know as a full Moon. But lunar eclipses do not occur every month because the Moon's orbit is tilted five degrees from Earth's orbit around the Sun. Without the tilt, lunar eclipses would occur every month.
Lunar and solar eclipses occur with about equal frequency. Lunar eclipses are more widely visible because Earth casts a much larger shadow on the Moon during a lunar eclipse than the Moon casts on Earth during a solar eclipse.
From which portion on the Earth can a total solar eclipse be seen?
Only viewers located in the path of the Moon's full shadow, its umbra, can see a total solar eclipse. The Moon's umbra travels eastward at about 1,700 km/h (1,056 mph). A total solar eclipse can last for several hours. Totality can range from a few seconds to 7.5 minutes.
What kind of image is formed by a pinhole camera?
A pinhole camera produces a real, inverted image which is smaller in size than the object.
On what principle does the action of a pinhole camera depend?
Pinhole cameras rely on the fact that light travels in straight lines – a principle called the rectilinear theory of light. This makes the image appear upside down in the camera. When the shutter is opened, light shines through to imprint an image on photographic paper or film placed at the back of the camera.
How does a change in the distance of the object from a pinhole camera affect the size of the image?
When you place an object in front of the pinhole camera, a clear image is formed on the screen. If the distance between the pinhole and screen is increased, the image size will increase and the image however will get less bright since the light spreads over a large area.
What happens when a ray of light falls on a plane mirror?
When a ray of light falls normally (or perpendicularly) on the surface of a plane mirror, it gets reflected along the same path because the angles of incidence and reflection are both equal to zero.