Test: Light Energy - Class 7 MCQ

A book is an example of a non-luminous object because it does not emit light on its own. It can only be seen when light from a luminous source reflects off its surface.

Lateral inversion occurs when light reflects off a plane mirror, causing the left side of an object to appear as the right side and vice versa. This effect is why our reflections appear reversed in mirrors.

The angle of incidence is defined as the angle formed between the incident ray and the normal line at the point of incidence. This angle is crucial in understanding the behavior of light when it strikes a surface.

The normal line is drawn perpendicular to the surface at the point of incidence. It serves as a reference point for measuring the angles of incidence and reflection, helping to determine how light behaves when it strikes a surface.

A divergent beam of light occurs when rays spread out from a single point in different directions. This type of beam is commonly seen in situations like a flashlight beam.

The primary colors of light are red, green, and blue. These colors can be combined in various ways to produce a wide range of other colors, including secondary colors like yellow and cyan.

An incident ray is the ray of light that approaches and strikes the surface of a mirror. Understanding incident rays is fundamental in studying the laws of reflection.

When light travels from one medium to another, it can either reflect, be absorbed, or refract. This behavior depends on the properties of the media involved, illustrating the complex nature of light interaction.

The sun is the main natural source of light for Earth, providing essential light and heat. It is a massive ball of burning gases that emits significant energy, making it crucial for life on our planet.

Color subtraction refers to the process by which objects absorb certain wavelengths of light and reflect others. The color perceived by our eyes is determined by the wavelengths that are reflected back.

The angle of reflection is always equal to the angle of incidence, according to the laws of reflection. This principle is fundamental in predicting how light will behave upon encountering reflective surfaces.

A parallel beam of light occurs when multiple rays travel in the same direction, maintaining their distance from each other. This type of beam is essential in various optical applications, including lasers.

Regular reflection occurs when parallel rays of light strike a smooth surface, such as a mirror, and reflect back as parallel rays. This clarity is essential for seeing detailed images.

When light hits a rough surface, it undergoes irregular reflection, scattering in various directions. This scattering allows us to see most objects around us, even if they don’t produce clear images.

Bioluminescence refers to the natural phenomenon where certain organisms, such as glowworms and fireflies, produce light through biochemical reactions. This capability is often used for attracting mates or prey.

A shadow is formed when an object blocks the path of light, creating a dark area behind it. Shadows illustrate the rectilinear propagation of light, demonstrating how light travels in straight lines.

Secondary colors are formed by mixing two primary colors. For example, mixing red and green light produces yellow, while mixing red and blue creates magenta.

Non-luminous objects are those that cannot produce their own light. They can only be seen when light from a luminous object reflects off them, such as the moon, which reflects sunlight.

Transparent materials are those that allow light to pass through completely, enabling clear visibility through them. Common examples include glass and clear water.

The speed of light is approximately 3 x 10^8 meters per second, or 300,000 kilometers per second. This incredible speed allows light to travel from the sun to Earth in about eight minutes.