Human Eye and Colourful World

Human Eye and Colourful World

• Options:
  a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
  c) Assertion (A) is true, but Reason (R) is false.
  d) Assertion (A) is false, but Reason (R) is true.

Question 1

Assertion (A): The human eye can perceive a limited range of wavelengths of light.
Reason (R): The visible spectrum of light ranges from approximately 400 nm to 700 nm.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The human eye is sensitive to only a small part of the electromagnetic spectrum, known as the visible spectrum, which ranges from 400 nm (violet) to 700 nm (red).

Question 2

Assertion (A): The cornea is responsible for most of the eye's focusing power.
Reason (R): The cornea has a constant curvature, allowing it to bend light effectively.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The cornea's fixed curvature provides a significant portion of the eye's total focusing power, refracting incoming light to focus on the retina.

Question 3

Assertion (A): The lens of the eye is biconvex in shape.
Reason (R): A biconvex lens converges light rays to a focal point.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The biconvex shape of the lens allows it to converge light rays onto the retina, enabling clear vision at various distances.

Question 4

Assertion (A): The retina contains photoreceptor cells called rods and cones.
Reason (R): Rods are responsible for color vision, while cones are responsible for low-light vision.

• Answer: b) Assertion (A) is true, but Reason (R) is false.
• Explanation: Rods are responsible for vision in dim light (night vision) and do not perceive color, while cones are responsible for color vision and function best in bright light.

Question 5

Assertion (A): Myopia is a condition where distant objects appear blurry.
Reason (R): Myopia occurs when the eyeball is too short.

• Answer: b) Assertion (A) is true, but Reason (R) is false.
• Explanation: Myopia, or nearsightedness, occurs when the eyeball is too long, causing light rays to converge before they reach the retina. This results in distant objects appearing blurry.

Question 6

Assertion (A): The blind spot is an area on the retina where no photoreceptor cells are present.
Reason (R): This is where the optic nerve exits the eye.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The blind spot, also known as the optic disc, lacks photoreceptors because this is the point where the optic nerve exits the eye, preventing the perception of light in this area.

Question 7

Assertion (A): The pupil of the eye adjusts its size in response to light intensity.
Reason (R): The iris is a muscular structure that controls the size of the pupil.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The iris regulates the amount of light entering the eye by changing the size of the pupil; it constricts in bright light and dilates in low light.

Question 8

Assertion (A): Color blindness is a genetic condition that affects the ability to perceive certain colors.
Reason (R): It occurs due to the absence or malfunction of cones in the retina.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: Color blindness typically results from the absence or dysfunction of specific types of cone cells that detect particular wavelengths of light, leading to difficulty in distinguishing certain colors.

Question 9

Assertion (A): The human eye can adapt to changing light conditions.
Reason (R): The adjustment of the pupil size is a mechanism for adaptation.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The eye's ability to adjust to varying light conditions through pupil size changes enables it to function effectively in both bright and dim environments.

Question 10

Assertion (A): Near vision requires the lens to become thicker.
Reason (R): The ciliary muscles contract to change the shape of the lens.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: When focusing on nearby objects, the ciliary muscles contract, allowing the lens to become thicker and refract light more sharply for clear near vision.

Question 11

Assertion (A): A person with hyperopia can see distant objects clearly but struggles with near objects.
Reason (R): Hyperopia occurs due to the eyeball being too short.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: Hyperopia, or farsightedness, occurs when the eyeball is shorter than normal, causing light rays to converge behind the retina, making near objects appear blurry.

Question 12

Assertion (A): The eye can focus on objects at different distances due to a process called accommodation.
Reason (R): Accommodation involves the adjustment of the lens shape by ciliary muscles.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: Accommodation allows the eye to focus on objects at varying distances by changing the shape of the lens, making it either thicker for near vision or thinner for distant vision.

Question 13

Assertion (A): The human eye can distinguish between millions of colors.
Reason (R): The eye has three types of cone cells sensitive to red, green, and blue light.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The combination of signals from the three types of cones enables the brain to perceive a wide range of colors through color mixing.

Question 14

Assertion (A): UV rays can damage the human eye.
Reason (R): The cornea and lens do not effectively filter UV radiation.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: Prolonged exposure to UV rays can lead to eye damage, including cataracts, as the cornea and lens allow some UV radiation to pass through.

Question 15

Assertion (A): The colors of objects can appear different under various lighting conditions.
Reason (R): The color perception of an object is dependent on the light source and its spectrum.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: Different light sources emit different wavelengths, affecting how colors are perceived; for instance, white light versus yellow light can change the appearance of colors.

Question 16

Assertion (A): The image formed on the retina is inverted.
Reason (R): Lenses refract light rays, causing them to cross before reaching the retina.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The optics of the eye cause light rays to converge and cross, resulting in an inverted image being projected onto the retina.

Question 17

Assertion (A): The color of an object is determined by the wavelengths of light it reflects.
Reason (R): An object appears colored because it absorbs certain wavelengths and reflects others.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The color perceived by the human eye depends on which wavelengths are reflected; for example, a red object reflects red wavelengths and absorbs others.

Question 18

Assertion (A): A rainbow is formed when sunlight is dispersed in raindrops.
Reason (R): Dispersion occurs when light passes from one medium to another at an angle.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: As sunlight enters raindrops, it refracts and disperses into its constituent colors, creating a rainbow.

Question 19

Assertion (A): The human eye has a blind spot due to the absence of rods and cones.
Reason (R): The optic nerve connects the eye to the brain, creating a gap in the retinal layer.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The point where the optic nerve exits the eye lacks photoreceptor cells, creating a blind spot in the visual field.

Question 20

Assertion (A): The color white is perceived when all colors of light are combined.
Reason (R): White light is the sum of all colors in the visible spectrum.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: When red, green, and blue light are combined in equal intensity, they produce white light, demonstrating the additive color mixing principle.