A student conducts an activity, where he took a naphthalene ball and burn it. He observed that it gives a yellow flame with lots of black smoke and sooty deposits around it. What type of hydrocarbon is it?

A student focussed the image of a candle flame on a white screen by placing the flame at various distances from a convex lens. He noted his observations as : What type of lens is a convex lens?

A student fixes a sheet of white paper on a drawing board. He places a bar magnet in the centre of it. He sprinkles some iron filings uniformly around the bar magnet. Then he taps the board gently and observes that the iron filings arrange themselves in particular pattern. What does the crowding of iron filings at the end of the magnet indicate?

A student constructed a model of box-type solar cooker. He used a transparent plastic sheet to cover the open face of the box. He found that this cooker does not function well. What modification should he make to enhance its efficiency ? Give reason.

A student warmed a neutral organic compound with some ethanoic acid and a little of concentrated sulphuric acid a test-tube. He observed that vapours having sweet smell (fruity smell) are evolved . (a) What types of functional group is present in this organic compound ? (b) Give the name and formula of one such organic compound .

A student fixes a sheet of white paper on a drawing board. He places a bar magnet in the centre of it. He sprinkles some iron filings uniformly around the bar magnet. Then he taps the board gently and observes that the iron filings arrange themselves in particular pattern. What do the lines along which the iron fillings align represent?

A student wants to project the image of a candle flame on a screen 60cm in front of a mirror by keeping the flame at a distance of 15 cm from its pole. (i) Write the type of mirror he should use. (ii) Find the linear magnification of the image produced. (iii) What is the distance between the object and its image ? (iv) Draw a ray diagram to show the image formation in this case.