Chemical Reactions and Equations — Science STD 10 — Question

How are waste products excreted in Amoeba?

An object is placed at a distance of 15 cm. from a convex lens of focal length 20 cm. List four characteristics (nature, position, etc.) of the image formed by the lens.

What is meant by:

1. A group, and
2. A period, in a periodic table?

Why does the Sun appear reddish early in the morning?

What names were given by Mendeleev to the then undiscovered elements.

1. Scandium.
2. Gallium, and
3. Germanium?

Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?

If current flows through two lamps arranged: (a) in series, (b) in parallel, and the filament of one lamps breaks, what happens to the other lamp ? Explain your answer.

Write two points of difference in the structures of diamond and graphite.

To find the image distance for varying object distances in case of a convex lens of focal length 15 cm, a student obtains on a screen a sharp image of a bright object by placing it at 20 cm distance from the lens. After that he gradually moves the object away from the lens and each time focuses the image on the screen.

1. In which direction-towards or away from the lens does he move the screen to focus the object?
2. How does the size of image change?
3. Approximately at what distance does he obtain the image of magnification -1?
4. How does the intensity of image change as the object moves farther and farther away from the lens?

Draw ray diagrams showing the image formation by a concave mirror when an object is placed:A little beyond centre of curvature of the mirror.