Test: Light Energy - Class 8 MCQ

The focus of a convex mirror is a virtual point from which light rays appear to diverge after reflection. Unlike concave mirrors, convex mirrors do not have a real focus where light converges.

We see the sun before it rises and after it sets due to the refraction of sunlight in the Earth's atmosphere. The bending of light rays as they pass through different air densities allows us to see the sun in positions that it has not yet reached or has already left.

A convex mirror is used for viewing a larger area while driving because it provides a wider field of view, allowing drivers to see more of the traffic behind them compared to a plane or concave mirror.

Violet light bends the most when passing through a prism due to having the highest refractive index among the colors in the visible spectrum, resulting in greater dispersion and creating a rainbow effect.

The constant ratio described by Snell's Law is known as the refractive index (\(\mu\)). It represents how much light bends when it passes between two different media, helping to understand the optical properties of materials.

Refraction causes submerged objects to appear closer to the surface than they actually are because the light rays bend away from the normal when they exit the water, altering our perception of depth.

The apparent depth of an object submerged in water appears shallower than its actual depth due to refraction. Light rays bend away from the normal when they exit the water, making the object seem closer to the surface than it really is.

A mirage occurs due to the refraction of light in layers of air at different temperatures, causing light rays to bend and create the illusion of water on hot surfaces, like sand in a desert.

When light moves from a rarer medium (like air) to a denser medium (like water), it bends towards the normal line, which is an imaginary line perpendicular to the surface at the point of incidence.

The angle of incidence is the angle formed between the incident ray, which is the incoming light, and the normal line at the point where the light strikes the surface. This angle is crucial in understanding how light behaves at interfaces.

The focal length (F) of a concave mirror is equal to half of its radius of curvature (R). This relationship helps in determining the focus of the mirror for various applications.

Refraction is the bending of light as it passes from one medium to another, changing its speed due to the different densities of the materials. For example, light bends when moving from air into water because water is denser than air.

A convex mirror always produces a virtual image that is upright and smaller than the object. This is beneficial for applications like rear-view mirrors in vehicles, allowing a wider field of view.

Light travels fastest in air compared to water and glass. The speed of light in air is approximately \(3 \times 10^8\) m/s, while it is slower in water and glass due to their higher densities.

Light rays that are parallel to the principal axis of a concave mirror converge at a point called the focus after reflection. This property is utilized in various applications such as shaving mirrors and reflectors in headlights.

A concave mirror forms a virtual image when the object is placed between the focus and the mirror. In this case, the rays appear to diverge from a point behind the mirror, creating an upright and larger image.

Real images are formed when light rays actually converge and can be projected onto a screen, while virtual images are formed when light rays appear to diverge and cannot be projected, as they are seen only in the mirror.

The incident ray is the ray of light that strikes the surface of a medium. Understanding the behavior of incident rays is essential for analyzing how light interacts with different surfaces and materials.

When light travels from a denser medium to a rarer medium, it bends away from the normal line. This behavior is crucial for understanding how optical devices function, such as lenses and prisms.

The term 'apparent depth' refers to how deep an object looks to an observer when viewed from above water. This depth appears shallower than the actual depth due to the refraction of light as it exits the water.