Light – Reflection and Refraction — Science STD 10 — Question

A student obtained a sharp image of a burning candle, placed at the farther end of a laboratory table, on a screen using a concave mirror. For getting better value of focal length of the mirror, the subject teacher suggested him for focusing a well illuminated distant object. What should the student do?

Which of the following ray diagrams is correct for the ray of light incident on a concave mirror as shown in Figure?

An object is placed 20cm in front of a plane mirror. The mirror is moved 2cm towards the object. The distance between the positions of the positions of the original and final images seen in the mirror is:

1. 2cm.
2. 4cm.
3. 10cm.
4. 22cm

A series of fast-moving still pictures can create an illusion of movement because:

A spherical mirror and a thin spherical lens have each a focal length of -15 cm. The mirror and the lens are likely to be.

An electric heater is rated at 2kW. Electrical energy costs Rs 4 per kWh. What is the cost of using the heater for 3 hours?

1. Rs 12.
2. Rs 24.
3. Rs 36.
4. Rs 48.

A student obtained a sharp image of a candle flame placed at the distant end of the laboratory table on a screen using a concave mirror to determine its focal length. The teacher suggested him to focus a distant building about 1 km far from the laboratory, for getting more correct value of the focal length. In order to focus the distant building on the same screen the student should slightly move the:

A converging lens is used to produce an image of an object on a screen,object on a screen. What change is needed for the image to be formed nearer to the lens?

1. Increase the focal length of the lens.
2. Insert a diverging lens between the lens and the screen.
3. Increase the distance of the object from the lens.
4. Move the object closer to the lens.

The medical condition in which the lens of the eye of a person becomes progressively cloudy resulting in blurred vision is called:

Magnification produced by a plane mirror is:

1. Less than one.
2. Greater than one.
3. Zero.
4. Equal to one.