9th Science II, 18th Chap. Observing space: Telescopes 🔭 1.

🙏 Thanks Google 🙏

To join our Whats App  group  महिती विज्ञानाची🎷 please touch the blue words👇

👉 माहिती विज्ञानाची 🎷

🌌 What is the difference between the sky and space?
Ans:

• Definition of the sky: The sky is the visible portion of atmosphere and the portion of the Earth's atmosphere that can be seen from the ground.
• The definition of Space: Space is everything beyond the sky which is a limitless expense in which the solar system, stars⭐, galaxies🌌, comets  ☄️ , and the endless universe exist. 
• The sky is a very tiny part of space. 
• Appears: The sky appears blue during the day, while space is always dark.
• Sound: Medium is necessary for the propagation of sound waves so sound can pass through the atmosphere/ sky. 
•  Sound waves cannot travel through space.
• Sunlight is scattered in the sky, while in space there is no scattering of sunlight takes place.

👓 What is meant by space observation? Why is it important?
Ans:
Definition:To observe distant planets, celestial bodies, galaxies, and other astronomical objects with the help of a telescope and satellites is known as space observation. 
These telescopes and satellites are either situated on the Earth or in space.
Importance of space observation:
Space observation is important for several reasons
1. Space observation gives us important information about the sun, stars, moons, comets planets, and other celestial bodies around the Earth. 
2. Space observation gives us information about different forms of light/radiation and The infinite extent of the universe. 
3. Space observation can help science go beyond its present boundaries. 
4. Modern telescopes and satellites fulfill the curiosity of knowledge to know the universe. 

👓 In 1608, spectacle maker and researcher, Hans Lippershey made the first telescope 🔭.

👏 Galileo made a telescope in
1609 and used it for space observations. He realized that there were many more stars than what could be seen with the naked eye. 
Using a telescope, Galileo also discovered the moons of Jupiter Ganymede, Europa, Io, Callisto, Rings of Saturn, the phases of Venus, the black spots on the sun, etc.

💡Different forms of light:
Ans: Light is an electromagnetic wave. Every wave has a characteristic wavelength. Our
eyes can see only that light which has wavelengths between 400 nm to 800 nm. Such light is
called visible radiation. However, there are electromagnetic waves of wavelengths other than the visible ones most of which we cannot ‘see’ as our eyes are not sensitive to them.

🦢 Optical telescopes/ refracting telescopes: 

Most optical telescopes are made
with two or more lenses. 
To collect the maximum amount of light coming from a heavenly object, the objective lens should be made as large as possible.
Using the light collected by the
objective a smaller lens called the eyepiece, produces a large image of the source.
 Light rays change their
direction as they enter a lens from the atmosphere and again when they enter the atmosphere after passing through the lens. This is called refraction. Hence such telescopes are called
refracting telescopes.

🦋 What are the limitations of refracting telescopes? 
Ans: 
 If we wish to obtain a bright image of a source by collecting the maximum possible light from the source, the objective lens must be made as large as possible. However, it is very difficult to make very large lenses. Also, large lenses are very
heavy and tend to get distorted.
2. As the objective and eyepiece are placed at the opposite ends of the telescope, the length of the telescope also increases with an increase in the size of the lenses and the telescope becomes difficult to manage.
3. The images formed by lenses have errors in colors. This is called chromatic aberration.


🔊 How we overcome the limitations of refracting telescopes? 
Ans: 
To overcome the difficulties of refracting telescopes, telescopes are now made using concave mirrors. 
 It is easier to make large mirrors as compared to making large lenses. 

Big mirrors can be made by combining several smaller
pieces. 

The weight of a large mirror too is less than that of a lens of the same size. 

The images formed by mirrors do not have errors of color. 

Only by using these large telescopes, we can see far-away stars and galaxies, which we could never have seen using our naked eyes. 

    *तुटून पुन्हा एकट्याने उभा राहिलेल्या, व्यक्तीला सहसा कोणाच्या आधाराची अथवा सहानुभूतीची गरज भासत नाही.*

               *कारण त्या व्यक्तीला स्वतःमध्ये असणार्‍या क्षमतांची जाणिव झालेली असते. म्हणून आयुष्यात स्वतःचा आधार स्वतःच झालेलं केव्हाही चांगलं असतं.*

               *आपला दिवस आनंदी जावो.*