Light: Shadows and Reflections - Class 7 Science Free MCQ Test with solutions

When an object is moved closer to the light source, its shadow becomes larger and less defined. This is because the angle at which light strikes the object changes, altering the projection of the shadow on the surface behind it.

A luminous object is one that emits its own light. A candle produces light through combustion, making it a perfect example of a luminous object. In contrast, the Moon reflects sunlight and is therefore classified as a non-luminous object.

A pinhole camera forms inverted images on a screen by allowing light rays to pass through a small hole. This technique captures the essence of the scene outside, resulting in an image that is reversed vertically, providing a unique perspective compared to mirrors.

Images formed by a plane mirror are laterally inverted, meaning that the left and right sides are reversed. For instance, if a person raises their left arm, the image in the mirror will show the right arm raised. This property is important for understanding how mirrors work in everyday life.

Shiny surfaces, such as polished mirrors, reflect light efficiently. This reflection allows for the creation of clear and bright images. In practical applications, such surfaces are used to redirect light, such as in mirrors found in various devices.

Rectilinear propagation refers to the property of light traveling in a straight line. This principle can be observed when light passes through aligned holes, forming distinct bright spots on a surface, demonstrating that light does not bend around obstacles under normal conditions.

A shadow is formed when an object obstructs light from reaching a surface. This requires a light source, an object to block the light, and a screen where the shadow appears. The characteristics of the shadow depend on the object's position relative to the light source and the screen.

LED lamps are significant because they consume less power and have a longer lifespan compared to traditional light sources. This not only reduces electricity costs but also lessens environmental impact, making them a preferred choice for sustainable lighting solutions.

Luminous objects, such as the Sun, stars, and fireflies, are capable of emitting their own light through various processes. In contrast, non-luminous objects do not produce their own light but instead reflect light from luminous sources. Understanding the distinction between these types of objects is essential in the study of light and its properties.

The image created by a plane mirror is virtual and the same size as the object placed in front of it. Unlike images formed by other optical devices, plane mirrors produce images that appear behind the mirror at the same distance as the object is in front of it. This property is essential for understanding how mirrors work in everyday life, such as in bathrooms and dressing rooms.

Translucent materials permit light to pass through but not in a manner that allows clear visibility. Examples include frosted glass and tracing paper, which create soft shadows and diffuse light. This property is useful in various applications, such as in lampshades and privacy windows, where light is desired without full visibility.

A periscope is designed to allow users to see objects that they cannot directly view, utilizing mirrors to reflect light around obstacles. This device is particularly useful in situations like submarines or military operations, where visibility is restricted. The arrangement of the mirrors in a periscope enables it to make use of light's properties for practical observation, demonstrating an ingenious application of optical principles.