Light - Free MCQ Practice Test with solutions, UPSC Lucent

The speed of light in a vacuum is approximately 300,000 kilometers per second (km/s).

When light passes from one medium to another (for example, from air to water) with a different refractive index, its speed changes. This change in speed causes the light ray to bend at the boundary between the two media. This bending of light is known as refraction.

Why the other options are incorrect:

• Reflection: Light bounces back from a surface.
• Scattering: Light spreads in different directions after hitting particles.
• Diffraction: Light bends around obstacles or spreads through narrow openings.

A convex lens is thicker at the center than at the edges and causes light to converge (focus).

In the visible light spectrum, blue light has the highest frequency among the options you provided. The order of increasing frequency in the visible light spectrum is generally: red, orange, yellow, green, blue, indigo, and violet. Therefore, blue light has a higher frequency than red, green, and yellow light.

When white light passes through a prism, it splits into different colors, which is known as dispersion.

The bending of light as it passes around the edges of an obstacle or through an opening is called diffraction.

The magnifying glass uses a convex lens. This type of lens is thicker in the middle and thinner at the edges. It helps to bend light rays in such a way that objects appear larger than they really are. Here are some key points about convex lenses:

• They converge light rays to a point.
• They create a larger image of the object being viewed.
• Commonly used in devices like magnifying glasses, cameras, and projectors.

In summary, a convex lens is essential for making objects look bigger, which is why it is used in a magnifying glass.

The distance between a lens and its focal point is called the focal length.

A green object reflects and transmits green light, while it absorbs other colors.

When light rays strike a rough surface, they undergo reflection in random directions.

The splitting of light into its constituent colors is observed in a rainbow.

Glass is the material that is most transparent to visible light.

Convex mirrors are used in rear view mirrors of motor vehicles. This is because they give an erect, virtual, full size diminished image of distant objects with a wider field of view.

Radioactivity is not a property of light. Reflection, diffraction, and interference are properties of light.

When light passes from a denser medium to a rarer medium, it speeds up.

Red light has the longest wavelength among the given options.

In farsightedness (hypermetropia), a person can see distant objects clearly but has difficulty seeing near objects. A convex lens converges the incoming light rays and helps focus the image of near objects on the retina, thereby correcting the defect.

The angle of incidence is equal to the angle of reflection according to the law of reflection.

The unit of luminous intensity is candela (cd).

A mirror is not a source of light. The Sun, Moon, and firefly are natural sources of light.