Carbon and its Compounds — Science STD 10 — Question

A doctor has prescribed a corrective lens of power, -1.5D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

What would happen to the number of grass plants and foxes if the number of rabbits:

1. Increased?
2. Decreased?

State any four characteristics of the image of an object formed by a plane mirror.

A person found that the cake prepared by him is hard and small in size. Which ingredient has he forgotten to add that would have caused the cake to rise and become light? Explain your answer.

An element Y is in second period and group 16 of the periodic table:

1. Is it a metal or non - metal?
2. What is the number of valence electrons in its atom?
3. What is its valency?
4. What is the name of the element?
5. What will be the formula of the compound formed by Y with sodium?

What is the role of seminal vesicles and prostrate gland in human male reproductive system?

To find-the image-distance for varying object-distances in case of a convex lens, a student obtains on a screen a sharp image of a bright object placed very far from the lens. After that he gradually moves the object towards the lens and each time focuses its image of the screen.

1. In which direction - towards or away from the lens, does he move the screen to focus the object?
2. What happens to the size of the image - does it increase or decrease?
3. What happen when he moves the object very close to the lens?

What is Maxwell’s corkscrew rule? For what purpose is it used?

Four resistances of 16 ohms each are connected in parallel. Four such combinations are connected in series. What is the total resistance?

The figure below shows a variable resistor in a dimmer switch.

How would you turn the switch to make the lights: (a) brighter, and(b) dimmer? Explain your answer