Maharashtra Board Class 9 Science Solution Chapter 18 – Observing Space : Telescopes
Balbharati Maharashtra Board Class 9 Science Solution Chapter 18: Observing Space : Telescopes. Marathi or English Medium Students of Class 9 get here Observing Space : Telescopes full Exercise Solution.
Std |
Maharashtra Class 9 |
Subject |
Science Solution |
Chapter |
Observing Space : Telescopes |
1.) Fill in the blanks with proper words.
Ans:
a) The wavelength of visible light is between 400 nm and 800 nm.
b) GMRT is used for radio waves.
c) A certain x-ray telescope is named after scientist Subramanian Chandrasekhar.
d) The first scientist to use a telescope for space observation was Galileo Galilei.
e) The biggest optical telescope in India is situated at Aryabhatta Research Institute of Experimental Sciences, Nainital.
2.) Form pairs.
Ans:
a) X-rays: Chandra
b) Optical telescope: Hubble telescope
c) Indian radio telescope: GMRT
d) Launching artificial satellites: ISRO
3.) What are the difficulties in using ground based optical telescope? How are they overcome?
Ans:
The difficulties in using ground based optical telescope are discussed as below:
- If we wish to obtain the bright image of the source by the collection of maximum light from the source then we have to made the objective lens as much large as possible. And it is very difficult to make large lenses which are very heavy and may get distort easily.
- When the objective and eyepiece are placed opposite to the ends of the telescope then length of the telescope also get increases as the size of the lens get increased and hence we can’t manage the telescope.
- There were errors of colours in the image formed by the lenses which is called as the chromatic aberration.
In order to overcome this difficulties telescope are mostly made with the help of concave mirror.
- When light is reflected front the mirror in telescope which are named as reflecting telescope.
- To get a bright image of source we require large mirrors but it is easy to made large mirrors than large lenses.
- By combining several small pieces we can made a large mirror. And most important thing is that the weight of big mirror is less than that of the same size lens.
- And images formed by the mirrors doesn’t have errors in colours. And by using this large telescope we can see the stars and galaxies which are far away from us and we couldn’t have seen them from our naked eyes.
4.) Which type of telescope can be made using a concave mirror, convex mirror, plane mirror and a lens? Draw diagram of these telescope.
Ans:
Reflecting types of mirrors can be made using convex mirror, concave mirror, plane mirror and a lenses which are of two types mainly Newtonian and Cassegarin.
1) Newtonian telescope:
- The figure shows the Newtonian telescope in which the light rays coming from space are reflected from the concave mirror and then get deflected again from the small plane mirror.
- Finally they get focused at the point which is lying on the perpendicular axis of the telescope cylinder.
- In this way, these rays will pass through the eyepiece and we can see the magnified image of the source.
2) The Cassegarin telescope:
- The figure below shows the Cassegarin telescope which also uses concave mirror.
- The light rays after reflection from concave mirror are again reflected back due to small convex mirror.
- These rays are then passed through the hole at the centre of concave mirror and after that through the eyepiece situated at the back of the mirror.
- And finally we can see the magnified image of the source through eyepiece.
5.) Study the figure and answer the following questions.
a) What type of telescope is shown in the figure?
Ans: The figure shows Newtonian telescope.
b) Label the main parts of the telescope.
Ans:
Following figure shows the neat labelled diagram of Newtonian telescope.
c) Which type of the mirror does the telescope use?
Ans:
In this telescope both plane mirror and the spherical mirror which is the concave mirror here are used.
d) What other type of telescope uses a curved mirror?
Ans:
Cassegarin telescope also uses the curved mirror.
e) Explain the working of the above telescope.
Ans:
- Reflecting types of mirrors can be made using convex mirror, concave mirror, plane mirror and a lenses which are of two types mainly Newtonian and Cassegarin.
- The figure shows the Newtonian telescope in which the light rays coming from space are reflected from the concave mirror and then get deflected again from the small plane mirror.
- Finally they get focused at the point which is lying on the perpendicular axis of the telescope cylinder.
- In this way, these rays will pass through the eyepiece and we can see the magnified image of the source.
6.) Answer the following questions.
a) Explain the construction of Galileo’s telescope.
Ans:
- In 1609, Galileo made a telescope and used it for space observations.
- It consists of two lenses which are located at the two ends of the tube and objective used is convex lenses while the eyepiece uses a concave lenses.
- The Galileo’s lenses provides us an erect image of the object.
- Galileo realized that there are number of stars which we could never seen through our naked eyes.
- Using Galileo’s telescope moons of Jupiter and black spots on the sun are also discovered.
b) Explain the construction of radio telescope.
Ans:
- In addition to visible radiation many heavenly objects also emits the radio waves which cannot visible to our eyes.
- To receive this rays special type of telescope is used called as radio telescope.
- Radio telescope is made from one or more dishes of parabolic shapes.
- The incident radio waves get reflected by these dishes and converges at the focus.
- While the radio receiver is placed at the focal point which gathers the information and which is passed on to a computer which on analysing it forms the image of the source.
- In this way, radio telescope works to form the image of the source.
c) Why are optical telescope located in uninhabited places in mountains?
Ans:
- The optical telescope located in uninhabited places in mountains because of the following reasons:
- We know that, when the light is absorbed by the atmosphere then the intensity of light decreases.
- As the atmospheric pressure and temperature changes then there will be change in path of the light due to which the image formed will be also shaken.
- As there sunlight is present during day hence we can’t use optical telescope in daytime.
- Because of the above all reasons optical telescope are located in uninhabited places on mountains to overcome the above mentioned problems.
d) Why can an x-ray telescope not be based on the earth?
Ans:
As the x-rays are blocked or absorbed by the atmosphere hence we can’t operate x-ray telescope on the earth’s surface.