Q28 of 48 Page 1

A student focussed the image of a distant object using a device 'X' on a white screen 'S' as shown in the figure. If the distance of the screen from the device is 40 cm, select the correct statement about the device.

The correct answer is: option (d).

The distant objects are focused at the point means the focal length will be equal to the distance between the screen and the mirror the focal length of the lens is 40 cm and since concave mirror converges the image , so the mirror used as the device is the concave mirror.

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26

A student prepared 20% sodium hydroxide solution in a beaker containing water. The observations noted by him are given below. 1

I. Sodium hydroxide is in the form of pellets.


II. It dissolves in water readily.


III. The beaker appears cold when touched from outside.


IV. The red litmus paper turns blue when dipped into the solution.


The correct observations are:

 27

Hard water required for an experiment is not available in a school laboratory. However, following salts are available in the laboratory. Select the salts which may be dissolved in water to make it hard for the experiment.

1. Calcium Sulphate


2. Sodium Sulphate


3. Calcium Chloride


4. Potassium Sulphate


5. Sodium Hydrogen Carbonate


6. Magnesium Chloride

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

 30

In an experiment to trace the path of a ray of light through a glass prism for different values of angle of incidence a student would find that the emergent ray: