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Question : 2
Total: 12
(a) (i) Distinguish between isotopes and isobars.
(ii) Two nuclei have different mass numbersA 1 A 2
OR
(b) (i) Name the factors on which photoelectric emission from a surface depends.
(ii) Define the term 'threshold frequency' for a photosensitive material. 2
(ii) Two nuclei have different mass numbers
OR
(b) (i) Name the factors on which photoelectric emission from a surface depends.
(ii) Define the term 'threshold frequency' for a photosensitive material. 2
Solution:
(i)
(ii) No, Only when the two nuclei have same atomic number then they are known as isotopes.Otherwise they may be isobars also. Isobars have same mass numbers.
OR
(b) (i) Factors on which photoelectric emission from a surface depends:
- Frequency of light
- Intensity of light
- Photosensitivity of the material
(ii) Threshold frequency: For a given photosensitive material, the minimum frequency of the incident radiation for which emission of photoelectrons takes place is called threshold frequency.
| Isotope | Isober |
| Same elements. | Different elements. |
| Same atomic number. | Different atomic number. |
| Different mass number. | Same mass number. |
| Numbers of protons are same in isotopes. | Numbers of protons are different in isobers. |
(ii) No, Only when the two nuclei have same atomic number then they are known as isotopes.Otherwise they may be isobars also. Isobars have same mass numbers.
OR
(b) (i) Factors on which photoelectric emission from a surface depends:
- Frequency of light
- Intensity of light
- Photosensitivity of the material
(ii) Threshold frequency: For a given photosensitive material, the minimum frequency of the incident radiation for which emission of photoelectrons takes place is called threshold frequency.
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