Reflection Of Light By Spherical Mirrors

To solve this problem, we need to understand the function of cone cells in the human eye.

1. Role of Cones in the Retina:
The retina of our eye contains two types of photoreceptor cells – rods and cones.
- Rods are responsible for vision in dim light and detecting the intensity of light.
- Cones are responsible for detecting **color** and function best in bright light.

2. Evaluating the Options:
(1) Intensity of light – Incorrect (function of rods)
(2) Colour – Correct ✅ (cones are responsible for color vision)
(3) Taste – Incorrect (not related to eye function)
(4) Smell – Incorrect (not related to eye function)

Final Answer:
The correct option is (B) Colour.

To solve the problem, we need to understand the behavior of a convex mirror.

1. Properties of a Convex Mirror:
A convex mirror always forms an image that has the following characteristics:

• The image is virtual.
• The image is always diminished (smaller than the object).
• The image is upright (erect).
• The image is formed behind the mirror, regardless of the object's distance.

2. Conclusion:
For a convex mirror, the size of the image is always diminished compared to the size of the object.

Final Answer:
The size of the image formed by a convex mirror is always .

To solve the problem, we need to identify the type of spherical mirror whose reflecting surface is curved outward.

1. Types of Spherical Mirrors:
There are two main types of spherical mirrors based on the direction of the curvature of their reflecting surfaces:

• Concave Mirror: The reflecting surface is curved inward (shaped like a bowl).
• Convex Mirror: The reflecting surface is curved outward (shaped like the outside of a sphere).

2. Conclusion:
The spherical mirror whose reflecting surface is curved outward is called a convex mirror.

Final Answer:
The correct answer is (A) Convex mirror.

To solve the problem, we need to determine the type of mirror used in a solar cooker.

1. Function of Mirrors in Solar Cookers:
In a solar cooker, the mirror is used to reflect sunlight and concentrate it at a focal point to generate heat. This heat is then used for cooking.

2. Type of Mirror Required:
A concave mirror is used in solar cookers because it can focus parallel rays of light (such as sunlight) to a single point (the focal point), allowing concentrated energy for cooking.

Final Answer:
The type of mirror used in a solar cooker is Concave (Option A).

To solve the problem, we need to find the focal length of a plano-convex lens, where is the radius of curvature and is the refractive index.

1. Understanding the Lens Formula:
For a plano-convex lens, the focal length can be derived using the lens maker's formula. For a plano-convex lens, the formula is:

Where:
- is the radius of curvature of the curved surface.
- is the refractive index of the material of the lens.

2. Deriving the Formula:
This formula is used for a lens where one side is flat (plano) and the other side is curved (convex), and it gives the relationship between the radius of curvature and the refractive index in determining the focal length.

3. Final Answer:
The focal length of the plano-convex lens is .

To solve the problem, we need to understand the behavior of a concave lens.

1. Magnification of a Concave Lens:
A concave lens always forms: - A virtual image, - An upright image, - A diminished image (smaller than the object).

2. Conclusion:
The magnification of a concave lens is always less than one because the image formed is smaller than the object.

Final Answer:
The magnification of a concave lens is always .

To solve the problem, we need to determine the type of image formed by a concave lens.

1. Understanding the Image Formation in a Concave Lens:
A concave lens is a diverging lens, which means it causes parallel light rays to diverge after passing through the lens. The image formed by a concave lens has the following characteristics:

• Erect: The image formed by a concave lens is always upright (erect), regardless of the object's position.
• Virtual: A concave lens forms a virtual image because the diverging rays appear to converge on the same side of the lens as the object.
• Smaller: The image formed is always smaller than the object, and it cannot be projected onto a screen.

2. Conclusion:
The correct description of the image formed by a concave lens is that it is erect and virtual.

Final Answer:
The correct answer is (A) Erect and virtual image.

To solve the problem, we need to understand how the focal length of a convex lens changes when placed in water.

1. Focal Length and Refractive Index:
The focal length of a lens is related to the refractive index of the lens material and the medium in which the lens is placed. The formula for the focal length of a lens in a medium is:



Where is the refractive index of the lens material, is the refractive index of the medium (water in this case), and is the radius of curvature of the lens.

2. Effect of Placing the Lens in Water:
When a convex lens is placed in water, the refractive index of the medium changes. Water has a refractive index of approximately 1.33, which is lower than the refractive index of glass (the common material of a convex lens).
Thus, the difference between the refractive index of the lens and the water decreases, resulting in an increase in the focal length.

Final Answer:
If a convex lens is placed in water, its focal length .

To solve the problem, we need to identify how many focal points a lens has.

1. Understanding Focal Points of a Lens:
Every lens has two focal points:

• One on the side of the incoming light (object side).
• One on the side of the outgoing light (image side).

2. Conclusion:
Thus, every lens has two focal points.

Final Answer:
The correct answer is (A) 2.

To solve the problem, we need to identify the point through which a parallel beam of light passes after passing through a convex lens.

1. Behavior of Light Passing Through a Convex Lens:
When parallel rays of light pass through a convex lens, they converge at a single point after refraction. This point is called the focus of the lens.

2. Understanding the Options:

Pole: The pole is the center of the lens and is not the point where parallel light rays converge after passing through the lens.

Centre of Curvature: The center of curvature is the center of the sphere of which the lens is a part, and it's not the point where the parallel rays focus.

Focus: The parallel rays converge at the focus of the lens. This is the correct answer.

None of the above: This option is incorrect because the correct answer is "Focus."

Final Answer:
The parallel beam of light after passing through a convex lens passes through a point called the Focus (Option C).