Iron nails were dipped in an aqueous solution of copper sulphate. after about 30 mintues, it was observed that the colour of the solution changed from

• Colourless to light green

• Blue to light green

• Blue to colurless

• Blue to colurless

A cleaned aluminium foil was placed in an aqueous solution of Zinc sulphate. when the aluminium foil was taken out of zinc sulphate solution after 15 minutes, its surface was found to be coated with a silvery grey deposit. From the above observation, it can be concluded than zinc

• Aluminium is more reactive than zinc.

• Zinc is more reactive than aluminium

• Zinc and aluminium both are equally reactive

• Zinc and aluminium both are equally reactive

Vapour of acetic acid smell

• Pungent like vinegar

• Sweet like rose

• Suffocating like sulphur dioxide

• Suffocating like sulphur dioxide

Acetic acid reacts with solid sodium hydrogen carbonate

• Slowly forming no gas

• Vigorously with effervescence

• Slowly without effervescence

• Slowly without effervescence

A student added acetic acid to test tubes I, II, III and IV containing the labelled substances and then brought a burning splinter near the mouth of each test tube.

To find the focal length of a concave mirror, Sita should choose which one of the following set-ups?

• A mirror holder and a screen holder

• A screen holder and a scale

• A mirror holder, a screen holder and a scale

• A mirror holder, a screen holder and a scale

By using a 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?

• Towards the screen

• Away from the screen

• Very far away from the screen

• Very far away from the screen

To determine the focal length of a convex lens by obtaining a sharp image of a distant object, the following steps were suggested which are not in proper sequence:

I. Hold the lens between the object and the screen.
II. Adjust the position of the lens to form a sharp image.
III. Select a suitable distant object.
IV. Measure the distance between the lens and the screen.

The correct sequence of steps to determine the focal length of the lens is,

• III, I, II IV

• III, I, IV, II

• III, IV, II, I

• III, IV, II, I

In these diagrams, the angle of refraction r has been correctly marked in which diagram?

• I

• II

• III

• III

For a ray of light passing through a glass slab, the lateral displacement was correctly measures as,

• AB

• PQ

• CD

• CD