STRUCTURE OF ATOM MATERIAL

 STRUCTURE OF ATOM

    1.  What is a spectrum?

A.  The group of wave lengths or frequencies is called a spectrum.

    2.  What is absorption spectrum?

A.  (i) The spectrum obtained when a substance absorbs energy is called absorption spectrum.

(ii) It contains dark lines on bright background.

    3.  What is emission spectrum?

A. (i) The spectrum formed by electro magnetic radiations emitted by a given source which is  in excited state is called emission spectrum.

(ii) It contains bright lines on a dark background.

    4.  Rainbow is an example for continuous spectrum – explain.

A. (i) When sun light dispersed through water droplets a bright colour spectrum is obtained.  It is called Rainbow.

(ii)  Rainbow consists of seven colours namely violet, indigo, blue, green, yellow, orange and

red (VIBGYOR).

(iii)  The colours spreading continuously and the intensity of each colour is different.

(iv)  So rainbow is an example for continuous spectrum.

5.  The wave length of a radio wave is 1.0m. Find its frequency?

A.                         wave length (h) = 1.0 m Speed of light (radio wave) c = 3 x 10⁸ m/s

Frequency (Ʋ) = ?

Formula :         c = Ʋ h Ʋ = ^c

λ

= 3 X 108

1.0

= 3 x 10⁸ Hz

    6.  What is electro magnetic wave?

A. The wave passing perpendicular to the electric field and magnetic field which are perpendicular  to each other is called electromagnetic wave.

    7.  Write the properties of electromagnetic wave.

A. (i) Electromagnetic wave : The wave passing perpendicular to the electric field and magnetic field which are perpendicular to each other is called electromagnetic wave.

(ii)  It can travel with the light speed c = 3 x 10⁸ m/s in the space.

(iii)  It can travel through vacuum also.

    8.  Draw the diagram of electromagnetic wave.

A.  Diagram of electromagnetic wave :

 Draw the diagram of electromagnetic spectrum.

19. 

Draw the diagram of electromagnetic spectrum.

A.  Diagram of electromagnetic spectrum.

10.     What is wave length?

A. (i) The distance between any two successive crests or troughs in a transverse wave is called wave length.

(ii)  It is denoted by “λ” .

(iii)  λ = ^c

Ʋ

Here; c = Speed of wave , Ʋ = Frequency of the wave

11.     What is wave frequency?

A. (i) The number of waves that pass by a given point in one second is called wave frequency.

(ii)  It is denoted by “Ʋ” .

(iii)  Ʋ = ^c

λ

Here; c = Speed of wave , λ = wave length

12.     What is speed of wave?

A. (i) The distance travelled by the wave in one second is called wave speed.

(ii)  It is denoted by “V” .

(iii)  V = Ʋλ

Here; Ʋ = Frequency of the wave, λ = wave length

13.     What is electromagnetic spectrum?

A. The entire range of electromagnetic wave frequencies is known as electromagnetic spectrum.

14.     Name some electromagnetic waves in electromagnetic spectrum.

A. Electromagnetic waves in electromagnetic spectrum :

(i)  Infrared rays

(ii)  Radio waves

(iii)  Micro waves

(iv) 

Visible light rays

(v)  UV- rays (ultra violet rays)

(vi)  x – rays

(vii)  Ɣ – rays

15.     What is visible light?

A. The range of wave lengths of light which can be seen with human eye is called visible light.

16.     Write Planck’s equation. Name the terms in it.

A. (i) Planck’s equation :          E    = h Ʋ

(ii) Here;                               E    = Energy of the radiation

h    = Planck’s constant = 6.626 x 10^-34 J-s

Ʋ = Frequency of radiation

17.     Write about Planck’s theory.

A. (i) Planck’s theory : The absorption or emission of energy by an atom is in the form of electromagnetic radiation only.

(ii)  The energy of the radiation is in multiples of hƲ only.

(iii)  It means the energy should be quantized.

(iv)  Formula for energy of radiation :        E     = h Ʋ

(v)  Here;                                E    = Energy of the radiation

h    = Planck’s constant = 6.626 x 10^-34 J-s

Ʋ = Frequency of radiation

18.   Write the Procedure of an activity to observe “different elements produce different colours on burning”.

A. Procedure of an activity to observe “different elements produce different colours on burning” :

Required material :         (i) Bunsen burner     (ii) Gas lighter

(iii) Platinum string (iv) Conc. Hydrochloric acid

(v) Watch glass         (vi) Glass rod

(vii) Cupric chloride (viii) Strontium chloride

Procedure :

(i)  Take 1g of Cupric chloride in watch glass.

(ii)  Add few drops of Conc. Hydrochloric acid.

(iii)  mix them with glass rod and make like paste.

(iv)  Lit the Bunsen burner.

(v)  Bend one end of platinum string like a loop.

(vi) 
Take the paste on the platinum loop and introduce it on the flame.

(vii)  We observe that Cupric chloride produce a green colour flame.

(viii)  If  we repeat the same with strontium chloride, we get crimson red flame.  So it is determined that different elements produce different colours on burning.