Q24 of 30 Page 1

In the figure given below, a narrow beam of white light is shown to pass through a triangular glass prism. After passing through the prism, it produces a spectrum XY on the screen.


(i) Name the phenomenon.


(ii) State the colors seen at X and Y.


(iii)Why do different colors of white light bend at different angles through a prism?


OR


(i) What is visible spectrum?


(ii) Why is red used as the stopping light at traffic signals?


(iii)Two triangular glass prisms are kept together connected through their rectangular side. A light beam is passed through one side of the combination. Will there be any dispersion? Justify your answer.


(i) The phenomenon involved is called dispersion of light. This dispersion of white light into a spectrum occurs because of the different colors present in white light are refracted by different amounts by the glass of the prism.


(ii)We know the sequence-VIGYOR


Hence the color X will be violet and Y will be red


(iii) White light consists of different colors, which bend through different angles with respect to the incidence beam due to variation in speed of light having different wavelengths.


OR


(i) The visible spectrum is that part of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation having this range of wavelengths is called visible light or light.


(ii) Red light has the longest wavelength. From VIBGYOR, the wavelength tends to increase from left to right, and RED is the last color in VIBGYOR with longest wavelength and colors with longest wavelength can be seen from long distances, hence red light is used in traffic signals.


(iii) When two glass prisms are kept together connected through their rectangular side then this combination behaves as a glass slab, and when a beam of light is allowed to pass through one side of the combination, then only white light is produced because when a ray of white light falls on the first prism, will disperse the light into its seven constituent colors.



Now when this band of seven colors, called a spectrum then falls on the second parallel placed adjacent side of the second prism this spectrum or the band of seven colors reunite and form the ray of white light.


More from this chapter

All 30 →
22

It is desired to obtain an erect image of an object, using concave mirror of focal length of 12 cm.

(i) What should be the range of the object distance in the above case?


(ii) Will the image be smaller or larger than the object? Draw a ray diagram to show the formation of image in this case.


(iii) Where will the image of this object be, if it is placed 24 cm in front of the mirror?


 23

Suppose your parents have constructed a two room house and you want that in the living room there should be a provision of one electric bulb, one electric fan, a refrigerator and a plug point for appliances of power up to 2 kilowatts. Draw a circuit diagram showing electric fuse and earthing as safety devices.

 25

(I)Metal X is found in nature as its sulphide XS. It is usedin the galvanisation of iron articles. Identify the metal X.How will you convert this sulphide ore into the metal?Explain with equations.

OR


(II)State the reason for the following:


(i) Aluminium oxide is called anamphoteric oxide.


(ii) An iron strip dipped in a blue copper sulphatesolution turns the blue solution pale green.


(iii) Hydrogen gas is not evolvedwhen most metals react with nitric acid.


(iv) Calcium does not occur in freestate in nature.


(v) Sodium or potassium metals are kept immersed underkerosene.


 26

The formulae of four organic compounds are given below:


(i) Which one of these compounds A, B, C or D is a saturated hydrocarbon?


(ii) Identify the organic acid and give its structural formula.


(iii) Which ofthe above compounds when heated at 443K in the presence of concentrated forms ethene as the major product? What is the role played byconcentrated in this reaction? Also write the chemical equationinvolved.


(iv) Give a chemical equation when B and C react with each other


in presence of concentrated. Name the major product formed andmention one of its important use.