1.
Concave lens is also known as converging lens.
Correct Answer
B. False
Explanation
The given statement is false. Concave lens is actually known as a diverging lens, not a converging lens. A concave lens causes parallel rays of light to spread out or diverge. It is thinner at the center and thicker at the edges, causing light rays to bend away from the center. This results in the image appearing smaller and virtual. On the other hand, a converging lens, also known as a convex lens, brings parallel rays of light together to a focal point, creating a real and magnified image.
2.
Any lens that is "thicker in the center" than on the edges is convex lens.
Correct Answer
A. True
Explanation
A convex lens is designed in a way that it is thicker in the center than on the edges. This shape causes the lens to converge light rays, which means it brings them closer together. This convergence allows the lens to focus light and create magnified, upright images. Therefore, it is correct to say that any lens that is "thicker in the center" than on the edges is a convex lens.
3.
Concave lens is thinner at its center than its edges.
Correct Answer
A. True
Explanation
A concave lens is thinner at its center than its edges because it is curved inward. This shape causes the light rays passing through the lens to diverge or spread out. As a result, the lens is thinner at the center to achieve the necessary curvature for the light to refract properly.
4.
Convex lens is also known as converging lens.
Correct Answer
A. True
Explanation
A convex lens is known as a converging lens because it causes parallel rays of light to converge or come together at a focal point. This is due to the shape of the lens, which is thicker in the middle and thinner at the edges. As a result, the lens bends the light rays inward, causing them to converge. This property of a convex lens allows it to form real and inverted images, making it a converging lens.
5.
Lenses are classified in to three.
Correct Answer
B. False
Explanation
The given statement is incorrect. Lenses are not classified into three categories. Lenses are typically classified into two main categories: converging lenses (also known as convex lenses) and diverging lenses (also known as concave lenses). These categories are based on the shape and curvature of the lens surface. Therefore, the correct answer is False.
6.
The point where all rays which enter the lens parallel to its axis are brought to a focus is called the ________ focus.
Correct Answer
A. Principal
Explanation
The point where all rays which enter the lens parallel to its axis are brought to a focus is called the principal focus. This is the point where the light rays converge after passing through the lens.
7.
how many varieties of lens are there?
Correct Answer
A. 2
Explanation
There are two varieties of lens.
8.
Mirrors and lenses both have the ability to reflect or ______ light.
Correct Answer
B. Refract
Explanation
Mirrors and lenses both have the ability to reflect or refract light. Refraction is the bending of light as it passes through a medium, such as a lens or a prism. This bending of light allows lenses to focus light and create images. Mirrors, on the other hand, reflect light by bouncing it off their surface. Therefore, the correct answer is refract.
9.
Lens that possesses at least one surface that curves ________ is a diverging lens.
Correct Answer
C. Inwards
Explanation
A lens that possesses at least one surface that curves inwards is a diverging lens. This is because a diverging lens is thinner in the middle and thicker at the edges, causing light rays to spread out or diverge when passing through it. The curvature of the lens surface inwards helps to achieve this diverging effect.
10.
Any lens that is thicker in the center than on the edges is generally described as a ______ lens.
Correct Answer
B. Convex
Explanation
A lens that is thicker in the center than on the edges is generally described as a convex lens. This is because a convex lens bulges outwards in the middle, causing light rays passing through it to converge or come together at a focal point. The thicker center of the lens causes the light to bend inward, resulting in the converging effect.
11.
The image formed by a _______ lens is virtual, upright, and smaller than the object.
Correct Answer
A. Concave
Explanation
A concave lens is thinner at the center and thicker at the edges. When light passes through a concave lens, it diverges or spreads out. This causes the image formed by a concave lens to be virtual, upright, and smaller than the object. The light rays do not actually converge to a point, but appear to come from a point behind the lens. Therefore, the image is virtual and cannot be projected onto a screen.
12.
The ______ formed by a concave lens is cannot be projected onto a screen.
Correct Answer
A. Image
Explanation
A concave lens is a diverging lens, meaning it spreads out light rays. When light rays pass through a concave lens, they diverge and do not converge to a point. As a result, the image formed by a concave lens is virtual, meaning it cannot be projected onto a screen. Therefore, the correct answer is "image".
13.
A similar point the same distance in front of the lens is called the len's _________ focus.
Correct Answer
B. Secondary
Explanation
When a point is at the same distance in front of the lens as the focal point, it is called the lens' secondary focus. This is because a lens has two focal points - the primary focus and the secondary focus. The primary focus is the point where parallel rays of light converge after passing through the lens, while the secondary focus is the point where parallel rays of light appear to diverge from after passing through the lens. Therefore, the correct answer is "secondary."
14.
The distance from the ______ of the lens to the principal focus is called the focal length.
Correct Answer
B. Center
Explanation
The distance from the center of the lens to the principal focus is called the focal length. This is because the focal length is a measure of how strongly the lens converges or diverges light rays, and it is determined by the curvature of the lens surfaces. The center of the lens is an important reference point for measuring the focal length because it is where the principal axis of the lens passes through and where the lens is symmetrical.
15.
A concave lens is thinner at its centre than at its edges, and is used to correct _____-sightedness.
Correct Answer
C. Short
Explanation
A concave lens is thinner at its center than at its edges, causing light rays to diverge when passing through it. This divergence helps to correct short-sightedness, also known as myopia. Short-sightedness occurs when the eyeball is too long or the cornea is too curved, causing light to focus in front of the retina instead of directly on it. By using a concave lens, the light rays are spread out before entering the eye, allowing them to focus properly on the retina and improving vision for near objects.