Test: Light, Sound and Force - 1 - Class 3 MCQ

• Shadow Direction: When Mr. X's shadow falls towards the east, it means that the sun is in the west.


• Shadow Position: The position of the sun can be determined by the direction of the shadow. If the shadow falls towards the east, then the sun must be in the west as the shadow is cast in the opposite direction of the sun.


• Time of Day: Typically, in the morning, the sun is in the east, and in the evening, the sun is in the west. Since Mr. X's shadow is falling towards the east, it indicates that it is either late afternoon or early evening.


• Conclusion: Therefore, based on the direction of Mr. X's shadow, we can conclude that the position of the sun at the moment is in the west.

• Shadow Size: When an object is closer to the source of light, it will cast a bigger shadow. This is because the closer an object is to the light source, the larger the shadow it will create.


• Light Rays: Light rays from the source spread out as they move away, so when an object is closer, it blocks more of these rays, creating a larger shadow.


• Distance: The distance between the object and the surface on which the shadow is cast also plays a role in determining the size of the shadow. The closer the object is to the surface, the larger the shadow will appear.


• Shape of the Shadow: The shape of the shadow may vary depending on the shape of the object and the angle at which the light is hitting it, but the size will generally be larger when the object is closer to the light source.

• Luminous Body: A luminous body is an object that emits light. Stars are examples of luminous bodies as they generate light and heat through nuclear fusion reactions in their cores.


• Plants: Plants are not luminous bodies. They do not emit their light.


• Books: Books are not luminous bodies. They do not produce light on their own.


• Star: Stars are luminous bodies. They emit light and heat due to the nuclear reactions happening in their cores.


• Moon: The moon is not a luminous body. It reflects light from the sun and does not generate its light.

• Light Energy: Light energy is the form of energy that enables us to see objects. When light reflects off an object and enters our eyes, it is converted into electrical signals that are sent to the brain, allowing us to perceive the object.


• Chemical Energy: Chemical energy is stored in the bonds of molecules and is released during chemical reactions. It is not directly responsible for enabling us to see objects.


• Sound Energy: Sound energy is produced by vibrations and is responsible for hearing, not for vision.


• Mechanical Energy: Mechanical energy is the energy associated with the motion and position of an object. It is not directly related to the sense of sight.

• Safety: Testing electrical appliances and switches with a tester ensures that they are functioning correctly and are safe to use.


• Avoid Electric Shock: Using a tester helps in identifying any faults or malfunctions in the appliance or switch, reducing the risk of electric shock.


• Proper Functionality: Testing with a tester ensures that the appliance or switch is working as intended and will not cause any electrical hazards.


• Prevent Damage: Regular testing with a tester can help in identifying any issues early on, preventing further damage to the appliance or switch.


• Compliance: Testing with a tester is often a requirement to ensure compliance with safety regulations and standards.

By using a tester to check electrical appliances and switches, you can ensure the safety of yourself and others around you, prevent damage to the appliances, and comply with safety standards.

• Opposing Force: The force that acts in the opposite direction to the motion of an object is called opposing force.


• Gravitational Force: Gravitational force is the force of attraction between two masses. It always acts downwards towards the center of the Earth.


• Frictional Force: Frictional force is the force that opposes the motion of an object when it is in contact with another surface. It acts in the opposite direction to the direction of motion.


• Muscular Force: Muscular force is the force generated by muscles in the body. It can be used to lift objects, push or pull things, and perform various physical activities.


• Electrostatic Force: Electrostatic force is the force between electrically charged objects. Like charges repel each other, and opposite charges attract each other.

From the given options, the force that is also known as the opposing force is the Frictional Force. Frictional force acts in the opposite direction to the motion of an object and opposes its movement. It is commonly experienced in everyday life when objects slide or move against each other.

• Mirror is an Opaque Object: Mirrors are considered opaque objects because they do not allow light to pass through them. When light hits the mirror, it is reflected back, creating an image. This property of reflecting light makes mirrors useful for various purposes like seeing ourselves, applying makeup, or even in scientific experiments.

Source of Light

• Option A: The image in Option A shows a light bulb, which is a source of light. When electricity passes through the filament inside the bulb, it emits light.


• Option B: The image in Option B shows a table fan, which is not a source of light. It is a device used for air circulation.


• Option C: The image in Option C shows a television, which is not a source of light. It is a device used for displaying images and videos.


• Option D: The correct answer is D, which states that all of the options are sources of light. This is incorrect because only Option A, the light bulb, is a source of light.