Physics assignment on the human eye and the colorful world, featuring questions about vision, optics, and color phenomena.
A document titled "Class: X Physics Assignment 5 Chapter: Human Eye and the Colorful World" containing a list of questions related to the human eye, vision, optics, and color perception.
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Show Answer Key & Explanations
Step-by-step solution for: SOLUTION: CBSE Class 10 Physics Human Eye Colorful World Worksheet ...
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Show Answer Key & Explanations
Step-by-step solution for: SOLUTION: CBSE Class 10 Physics Human Eye Colorful World Worksheet ...
1. The power of accommodation of the eye is its ability to adjust its focal length by changing the curvature of the eye lens, allowing it to focus on objects at varying distances.
2. a) Persistence of vision: The phenomenon where the impression of an image formed on the retina persists for about 1/16th of a second after the object is removed.
b) Far point of the eye: The farthest point from the eye at which an object can be seen clearly without strain; for a normal eye, it is at infinity.
c) Near point of the eye: The closest point to the eye at which an object can be seen clearly; for a normal eye, it is approximately 25 cm.
d) Least distance of distinct vision: The minimum distance at which an object can be seen clearly without strain; typically 25 cm for a normal adult eye.
3. When looking at a distant object, the ciliary muscles are relaxed, causing the eye lens to become thinner and flatter, which increases its focal length.
4. When entering a darkened cinema hall from bright light, the pupils need time to dilate (widen) to allow more light into the eyes, enabling clear vision in low-light conditions.
5. The student is suffering from myopia (nearsightedness). It can be corrected using a concave lens that diverges incoming light rays so that the image forms correctly on the retina. (Ray diagram would show parallel rays from a distant object converging in front of the retina without correction, and with a concave lens, they converge on the retina.)
6. As the object distance increases, the image distance decreases slightly, but remains nearly constant at the retina’s position due to the eye’s accommodation mechanism adjusting the lens’s focal length.
7. Dispersion is the splitting of white light into its constituent colors (VIBGYOR) when it passes through a prism, due to different wavelengths being refracted by different amounts.
8. Different colors deviate at different angles because each color has a different wavelength, and the refractive index of the prism material varies with wavelength (shorter wavelengths like violet bend more than longer wavelengths like red).
9. We see colors because different objects reflect specific wavelengths of visible light. Our retina contains cone cells sensitive to red, green, and blue light, which send signals to the brain to interpret the combination as a particular color.
10. To an astronaut in space, the sky appears dark because there is no atmosphere to scatter sunlight; thus, no scattered light reaches the eyes, leaving the background black.
11. The sun appears reddish early in the morning because sunlight travels through a thicker layer of atmosphere, scattering shorter wavelengths (blue, green) away, while longer wavelengths (red, orange) reach our eyes.
12. A rainbow is formed when sunlight enters water droplets, undergoes refraction, internal reflection, and then refraction again as it exits, dispersing into its component colors. An observer sees a circular arc of colors with red on the outer edge and violet on the inner edge.
13. Twinkling of stars is caused by atmospheric refraction. As starlight passes through layers of air with varying densities, it bends continuously, causing apparent fluctuations in brightness and position.
14. Danger signal lights are red because red light has the longest wavelength among visible colors and scatters the least, allowing it to travel farther through fog, dust, or rain without significant loss of intensity.
15. From a rainbow’s formation, we learn that sunlight is composed of multiple colors (dispersion), and that water droplets act as prisms to separate these colors via refraction and reflection.
16. The sun appears red at sunrise and sunset because its light passes through a greater thickness of atmosphere, scattering away shorter wavelengths and allowing only longer red wavelengths to reach the observer.
17. Bifocal lenses have two distinct optical powers: the upper part for distance vision and the lower part for near vision. They are required by people suffering from presbyopia (age-related loss of accommodation).
18. For a myopic person whose far point is 1.2 m, a concave lens is needed. Power = -1 / far point (in meters) = -1 / 1.2 ≈ -0.83 D.
19. For a hypermetropic eye with near point at 75 cm, to read at 25 cm: Using lens formula, 1/f = 1/v - 1/u → 1/f = 1/(-75) - 1/(-25) = 1/25 - 1/75 = (3-1)/75 = 2/75 → f = 37.5 cm. Power = 100 / f(cm) = 100 / 37.5 ≈ +2.67 D.
20. For a myopic person with lens power -0.5 D, focal length f = 1 / P = 1 / (-0.5) = -2 m. The far point is 2 meters.
21. Object distance u = -20 cm, near point v = -30 cm. Using lens formula: 1/f = 1/v - 1/u = 1/(-30) - 1/(-20) = -1/30 + 1/20 = ( -2 + 3 ) / 60 = 1/60 → f = 60 cm. Power = 100 / 60 ≈ +1.67 D.
22. Far point = 1.5 m → focal length f = -1.5 m. Power = 1 / f = 1 / (-1.5) ≈ -0.67 D. Concave lens.
23. Focal length of concave lens = -10 cm. Power = 100 / f(cm) = 100 / (-10) = -10 D.
2. a) Persistence of vision: The phenomenon where the impression of an image formed on the retina persists for about 1/16th of a second after the object is removed.
b) Far point of the eye: The farthest point from the eye at which an object can be seen clearly without strain; for a normal eye, it is at infinity.
c) Near point of the eye: The closest point to the eye at which an object can be seen clearly; for a normal eye, it is approximately 25 cm.
d) Least distance of distinct vision: The minimum distance at which an object can be seen clearly without strain; typically 25 cm for a normal adult eye.
3. When looking at a distant object, the ciliary muscles are relaxed, causing the eye lens to become thinner and flatter, which increases its focal length.
4. When entering a darkened cinema hall from bright light, the pupils need time to dilate (widen) to allow more light into the eyes, enabling clear vision in low-light conditions.
5. The student is suffering from myopia (nearsightedness). It can be corrected using a concave lens that diverges incoming light rays so that the image forms correctly on the retina. (Ray diagram would show parallel rays from a distant object converging in front of the retina without correction, and with a concave lens, they converge on the retina.)
6. As the object distance increases, the image distance decreases slightly, but remains nearly constant at the retina’s position due to the eye’s accommodation mechanism adjusting the lens’s focal length.
7. Dispersion is the splitting of white light into its constituent colors (VIBGYOR) when it passes through a prism, due to different wavelengths being refracted by different amounts.
8. Different colors deviate at different angles because each color has a different wavelength, and the refractive index of the prism material varies with wavelength (shorter wavelengths like violet bend more than longer wavelengths like red).
9. We see colors because different objects reflect specific wavelengths of visible light. Our retina contains cone cells sensitive to red, green, and blue light, which send signals to the brain to interpret the combination as a particular color.
10. To an astronaut in space, the sky appears dark because there is no atmosphere to scatter sunlight; thus, no scattered light reaches the eyes, leaving the background black.
11. The sun appears reddish early in the morning because sunlight travels through a thicker layer of atmosphere, scattering shorter wavelengths (blue, green) away, while longer wavelengths (red, orange) reach our eyes.
12. A rainbow is formed when sunlight enters water droplets, undergoes refraction, internal reflection, and then refraction again as it exits, dispersing into its component colors. An observer sees a circular arc of colors with red on the outer edge and violet on the inner edge.
13. Twinkling of stars is caused by atmospheric refraction. As starlight passes through layers of air with varying densities, it bends continuously, causing apparent fluctuations in brightness and position.
14. Danger signal lights are red because red light has the longest wavelength among visible colors and scatters the least, allowing it to travel farther through fog, dust, or rain without significant loss of intensity.
15. From a rainbow’s formation, we learn that sunlight is composed of multiple colors (dispersion), and that water droplets act as prisms to separate these colors via refraction and reflection.
16. The sun appears red at sunrise and sunset because its light passes through a greater thickness of atmosphere, scattering away shorter wavelengths and allowing only longer red wavelengths to reach the observer.
17. Bifocal lenses have two distinct optical powers: the upper part for distance vision and the lower part for near vision. They are required by people suffering from presbyopia (age-related loss of accommodation).
18. For a myopic person whose far point is 1.2 m, a concave lens is needed. Power = -1 / far point (in meters) = -1 / 1.2 ≈ -0.83 D.
19. For a hypermetropic eye with near point at 75 cm, to read at 25 cm: Using lens formula, 1/f = 1/v - 1/u → 1/f = 1/(-75) - 1/(-25) = 1/25 - 1/75 = (3-1)/75 = 2/75 → f = 37.5 cm. Power = 100 / f(cm) = 100 / 37.5 ≈ +2.67 D.
20. For a myopic person with lens power -0.5 D, focal length f = 1 / P = 1 / (-0.5) = -2 m. The far point is 2 meters.
21. Object distance u = -20 cm, near point v = -30 cm. Using lens formula: 1/f = 1/v - 1/u = 1/(-30) - 1/(-20) = -1/30 + 1/20 = ( -2 + 3 ) / 60 = 1/60 → f = 60 cm. Power = 100 / 60 ≈ +1.67 D.
22. Far point = 1.5 m → focal length f = -1.5 m. Power = 1 / f = 1 / (-1.5) ≈ -0.67 D. Concave lens.
23. Focal length of concave lens = -10 cm. Power = 100 / f(cm) = 100 / (-10) = -10 D.
Parent Tip: Review the logic above to help your child master the concept of human eye worksheet.
