The Class 10 is an important year in a student’s life and Maharashtra State Board Science 1 is one of the subjects that require dedication, hard work, and practice. It’s a subject where you can score well if you are well-versed with the concepts, remember the important formulas and solving methods, and have done an ample amount of practice. Worry not! Home Revise is here to make your Class 10 journey even easier. It’s essential for students to have the right study material and notes to prepare for their board examinations, and through Home Revise, you can cover all the fundamental topics in the subject and the complete Maharashtra State Board Class 10 Science 1 Book syllabus.
1. Prove that a rainbow is the combined effect of the refraction, dispersion, and total internal reflection of light.
Answer: After rainfall or shower, the tiny droplets of water found in the atmosphere acts as a prism for the rays that are coming from the sun so that the rays that enter the droplets are reflected and dispersed to produce a spectrum of light, which takes on the shape of an arc with seven colours. This is a naturally beautiful phenomenon, called the Rainbow. Thus, it is seen that the rainbow is the result of a combination of reflection, refraction and dispersion of light. The rainbows caused by sunlight are always found to arise opposite the sun in the sky. Even though the rainbow is formed in a full circle in the sky, we only get to view an arc that is created by illuminated droplets.
2. What is the reason for the twinkling of stars?
Answer: Stars are self luminous and can be seen at night, despite the absence of sunlight. They appear to us as point sources as they are at a very large distance from us. Now, as the density of the air increases along with lowering the height above the surface of the earth, the refractive index also increases. Starlight coming towards us travels from rarer medium to denser medium and constantly bends towards the normal, thus making the star appear to be higher in the sky as compared to its actual position. The motion of the atmospheric air as well as the changing air density and temperature result in changing of the apparent position of the star. This leads to the continuously changing refractive index of air. As a result, the position and brightness of the star also keep changing continuously and the star appears as if it is twinkling.
3. If the speed of light in a medium is 1.5 x 108 m/s, what is the absolute refractive index of the medium?
Answer: Data given is speed of light in a medium (v) = 1.5 x 108 m/s
And assume that speed of light in vacuum as c= 3 x 108 m/s
Then, absolute refractive index of the medium (n) = c/v
Hence, n= (3 x 108 ) / (1.5 x 108 ) = 3 / 1.5 = 2
Thus, the absolute refractive index of the medium is 2.
4. If the absolute refractive indices of glass and water are 3/2 and 4/3 respectively, what is the refractive index of glass with respect to water?
Answer: Assume, Refractive index (n) = c (velocity of light in vacuum) / v (velocity of light in a medium)
Then, 4/3 = c/ v1 (velocity of light in water) and 3/ 2 = c/ v2 (velocity of light in glass)
Now, velocity of light in water / velocity of light in glass = (c/ v1 ) / (c/ v2 ) = (4/3) / (3/2)
We get v2 / v1 = 8/9
Thus, v1 / v2 = 9/8
So, 9/8 is the refractive index of glass with respect to water.
5. What is refraction of light and dispersion of light?
Answer: The phenomenon of light changing its direction when going from one transparent medium to another transparent medium is known as the refraction of light. The velocity of light rays of all frequencies is the same. The velocity of light in a medium is dependent on the frequency of light and thus, different colours travel with different velocity. Hence, the refractive index of a medium is different for different colours. Thus, even when white light enters a single medium like glass, the angles of refraction are different for different colours. For this reason, when the white light coming from the Sun through air enters any refracting medium, it emerges as a spectrum of seven colours. So, dispersion of light is the process of separation of light into its component colours while passing through a medium.
6. How is Refraction of light in different media? Draw images.
Answer: Here, you can see the refraction of light in different media:
Finally,
7. Give a reason why planets do not appear to be twinkling like the stars?
Answer: Twinkling of stars is not visible to us, because planets are closer to us as compared to the stars. Owing to this, the planets do not appear as point sources, but are visible as a collection of point sources. Now, as changes are applied in the atmospheric refractive index the position as well as the brightness of individual point source change. However, the average position and total average brightness remain constant and so the planets do not twinkle.
8. What is known as partial reflection?
Answer: It is seen that the light that enters a rarer medium from a denser medium is partially reflected i.e. part of the light gets reflected and comes back into the denser medium, according to the laws of reflection. This is known as partial reflection. Rest of the light gets refracted and goes into the rarer medium.
9. The absolute refractive index of water is 1.36. What is the velocity of light in water? (velocity of light in vacuum 3 x108 m/s).
Answer: We have, Velocity of light in vacuum (V1 ) = 3 x108 and n= 1.36
Now, suppose n = V1 / V2
Then, 1.36 = (3 x108 ) / V2
Therefore, V2 = (3 x108 ) / 1.36
Thus, V2 = 2.21 ×108 m/s.
10. Light travels with a velocity 1.5 x 108 m/s in a medium. On entering the second medium its velocity becomes 0.75 x 108 m/s. What is the refractive index of the second medium with respect to the first medium?
Answer: V1 = 1.5 x108 m/s and V2 = 0.75 x108 m/s are given
Hence, 2 n1 = ?
Apply the equation 2 n1 = V1 / V2
Replacing with values
2 n1 = (1.5 x108 ) / (0.75 x108 ) 1.5/ 0.75 = 2.