What happens when ferrous sulphate crystals are heated?

Analyse the following observation table showing variation of image distance (v) with object distance (u) in case of a convex lens and answer the Question s that follow, without doing any calculations:

i. What is the focal length of the convex lens? Give reason in support of your answer.

ii. Write the serial number of the observation which is not correct. How did you arrive at this conclusion?

iii. Take an appropriate scale to draw ray diagram for the observation at S.No.4 and find the approximate value of magnification.

OR

i. To construct a ray diagram we use two rays which are so chosen that it is easy to know their directions after reflection from the mirror. List two such rays and state the path of these rays after reflection in case of concave mirrors. Use these two rays and draw ray diagram to locate the image of an object placed between pole and focus of a concave mirror.

ii. A concave mirror produces three times magnified image on a screen. If the object is place 20 cm in front of the mirror, how far is the screen from the object?

i. For observation no.3 clearly shows that the focal length is + 15 cm.

(i) The electric power consumed by a device may be calculated by using either of the two expressions P = I2R or P = V2/R. The first expression indicates that it is directly proportional to R whereas the second expression indicates inverse proportionality. How can the seemingly different dependence of P on R in these expressions be explained?

ii. Explain the following:

(a) Why is tungsten used almost exclusively for filament of electric lamps?

(b) Why are copper and aluminium wires usually used for electricity transmission?

Iron filings were added to a solution of copper sulphate. After 10 minutes, it was observed that the blue colour of the solution changes and a layer gets deposited or iron filings. What is the colour of the solution and the layer deposited?

Which light influences the opening of stomata?