Human Eye and Colourful World — Science STD 10 — Question

An image is formed on the retina. This is due to:

If the index finger points towards the north and the middle finger towards the east, when using Flemings left-hand rule, what will be the direction of motion or that of the force acting on the conductor?

By using convex lens, a student obtained a sharp image of his class-room window grill on a screen. In which direction should he move the lens to "focus a distant tree instead of the grill?

The 'coolants' which can be used in the reactor of a nuclear power station are:

1. Liquid mercury and nitrogen dioxide.
2. Liquid sodium and carbon dioxide.
3. Liquid ammonia and carbon monoxide.
4. Liquid boron and uranium oxide.

A convex lens produces a magnification of +5. The object is placed:

Select from the following the best set-up for tracing the path of a ray of light through a rectangular glass slab:

Assertion : A compass needle is placed near a current carrying wire. The deflection of the compass needle decreases when the magnitude of the current in the wire is increased.
Reason : The strength of a magnetic field at a point near the conductor increases on increasing the current.

If a magnification of, -1(minus 1) is obtained by using a converging lens, then the object has to be placed:

1. Within f.
2. At 2f.
3. Beyond 2f.
4. At infinity.

The heat produced in a wire of resistance 'x' when a current 'y' flows through it in time 'z' is given by:

A child is standing in front of a magic mirror. She finds the image of her head bigger, the middle portion of her body of the same size and that of the legs smaller. The following is the order of combinations for the magic mirror from the top.

1. Plane, convex and concave.
2. Convex, concave and plane.
3. Concave, plane and convex.
4. Convex, plane and concave.