Class 8 Science : Practice Questions and Answers

The angle of reflection is defined as the angle between the reflected ray and the normal (a line perpendicular to the surface). According to the law of reflection, the angle of incidence equals the angle of reflection.

Earthquakes are caused by the movement of tectonic plates beneath the Earth's surface. These movements release energy, leading to shaking of the ground.

When light strikes a mirror, it is reflected back. The angle at which the light hits the mirror equals the angle at which it is reflected, as per the law of reflection.

A rainbow forms due to the refraction (bending) and dispersion (spreading) of light as it passes through water droplets in the atmosphere, splitting the light into its color spectrum.

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

Clouds form when water vapor in the air cools and condenses into tiny droplets or ice crystals, which group together to form visible clouds.

An earthquake is a natural event caused by the sudden release of energy from the Earth's crust, resulting in shaking or movement of the ground surface.

Lightning travels at the speed of light, which is faster than sound. Therefore, we see the flash of lightning before hearing the sound of thunder.

During electrolysis, the cathode is where reduction occurs. This is because the cathode is negatively charged, attracting positive ions which gain electrons.

Electrolysis is a process in which an electric current is used to break down a compound into its components, such as breaking water into hydrogen and oxygen.

When an electric current passes through a solution, it can cause a chemical reaction known as electrolysis, where compounds are broken down into their elements.

An echo is the reflection of sound waves off a surface. When the sound waves hit a reflective surface, they bounce back toward the listener, creating a delayed sound that is perceived as an echo.

The frequency of the sound wave does not affect its speed. However, the speed of sound is influenced by the temperature, type, and density of the medium through which it travels.

Sound is a form of mechanical energy created by the vibration of objects. These vibrations generate sound waves that travel through a medium (such as air, water, or solids) and can be heard when they reach the human ear.

Rolling friction occurs when an object, such as a wheel or a ball, rolls over a surface. The contact between the rolling object and the surface causes resistance, but it is generally less than sliding friction.

The two main types of friction are static friction (the force that resists the initiation of motion) and sliding friction (the force that opposes the motion of an object sliding over a surface). Both play a role in everyday activities such as walking or driving.

Pressure is inversely proportional to the area over which a force is applied. If the area of contact increases, the pressure decreases because the same force is spread over a larger area.

Frictional force is a contact force because it occurs when two surfaces rub against each other. It acts to oppose the motion of an object and is influenced by the texture and type of materials in contact.

Force is a push or pull exerted on an object that can cause it to move, stop, or change its direction. It is measured in newtons and can affect an object's speed, direction, or shape.

One of the primary characteristics of male puberty is the deepening of the voice. This occurs due to the growth and thickening of the larynx and vocal cords, triggered by hormones like testosterone.