18. Observing Space: Telescopes
# Different forms of light –
1. Light is an electromagnetic wave.
2. Electromagnetic waves are classified into 𝛾 −rays, 𝑋 −rays, ultraviolet rays, visible
light, infrared rays, microwaves and radiowaves.
3. Wavelength of 𝛾 −rays is very small and that of radiowaves is large.
4. Wavelength of visible light is from 400𝑛𝑚 to 800𝑛𝑚.
# Telescope –
1. An optical instrument used to observe astronomical objects is called telescope.
2. Lippershey made first telescope in 1608.
3. In 1609, Galileo made a telescope and used it for space observation.
4. ISRO was established in 1969. Till date, ISRO has launched large number of artificial
satellites.
5. In 1990, NASA launched an optical telescope into space. This is called Hubble
telescope.
6. In 1999, NASA launched 𝑋 −ray telescope into space. This is called Chandra. The
telescope is named after the famous Indian scientist Subramanian Chandrashekhar.
7. The Indian radio telescope called Giant Meterwave Radio Telescope (GMRT) has been
erected at Narayangaon near Pune.
8. The biggest telescope in India is situated in Aryabhatt Research Institute of
Experimental Sciences at Nainital. This telescope has a mirror of 3.6𝑚 diameter.
# Galileo Telescope –
1. In 1609, Galileo made a telescope and used it for space observation.
2. It is a simple refracting telescope.
3. It consists of two convex lenses fixed at either end of a hollow metal tube.
4. The lens towards the object is called objective and that towards the eye is called
eyepiece. Objective is larger than eyepiece.
5. The distance between the lenses can be adjusted by rack and pinion arrangement.
6. Galileo discovered the moons of Jupiter, the black spots on the sun, etc. by using
this telescope.
# Types of telescopes –
1. Main types of telescopes are optical telescope and radio telescope.
2. Optical telescopes are divided into refracting telescope and reflecting telescope.
3. Reflecting telescopes are Newtonian telescope and Cassegrain telescope.
4. Special type of telescope is used to receive radio waves that are invisible to eyes is
called radio telescope.
5. 𝛾 − ray telescope, 𝑋 − ray telescope, ultraviolet telescope, infrared telescope,
microwave telescope, GMRT are the types of radio telescope.
Mr. Naik’s Theory Notes 1 Observing Space: Telescopes
# Different forms of light –
1. Light is an electromagnetic wave.
2. Electromagnetic waves are classified into 𝛾 −rays, 𝑋 −rays, ultraviolet rays, visible
light, infrared rays, microwaves and radiowaves.
3. Wavelength of 𝛾 −rays is very small and that of radiowaves is large.
4. Wavelength of visible light is from 400𝑛𝑚 to 800𝑛𝑚.
# Telescope –
1. An optical instrument used to observe astronomical objects is called telescope.
2. Lippershey made first telescope in 1608.
3. In 1609, Galileo made a telescope and used it for space observation.
4. ISRO was established in 1969. Till date, ISRO has launched large number of artificial
satellites.
5. In 1990, NASA launched an optical telescope into space. This is called Hubble
telescope.
6. In 1999, NASA launched 𝑋 −ray telescope into space. This is called Chandra. The
telescope is named after the famous Indian scientist Subramanian Chandrashekhar.
7. The Indian radio telescope called Giant Meterwave Radio Telescope (GMRT) has been
erected at Narayangaon near Pune.
8. The biggest telescope in India is situated in Aryabhatt Research Institute of
Experimental Sciences at Nainital. This telescope has a mirror of 3.6𝑚 diameter.
# Galileo Telescope –
1. In 1609, Galileo made a telescope and used it for space observation.
2. It is a simple refracting telescope.
3. It consists of two convex lenses fixed at either end of a hollow metal tube.
4. The lens towards the object is called objective and that towards the eye is called
eyepiece. Objective is larger than eyepiece.
5. The distance between the lenses can be adjusted by rack and pinion arrangement.
6. Galileo discovered the moons of Jupiter, the black spots on the sun, etc. by using
this telescope.
# Types of telescopes –
1. Main types of telescopes are optical telescope and radio telescope.
2. Optical telescopes are divided into refracting telescope and reflecting telescope.
3. Reflecting telescopes are Newtonian telescope and Cassegrain telescope.
4. Special type of telescope is used to receive radio waves that are invisible to eyes is
called radio telescope.
5. 𝛾 − ray telescope, 𝑋 − ray telescope, ultraviolet telescope, infrared telescope,
microwave telescope, GMRT are the types of radio telescope.
Mr. Naik’s Theory Notes 1 Observing Space: Telescopes
