The photoelectric effect is one of the most revolutionary phenomena in physics that shattered classical wave theory and laid the foundation for quantum mechanics. Discovered by Heinrich Hertz in 1887 and explained by Albert Einstein in 1905 (for which he won the Nobel Prize), this effect demonstrates the particle nature of light. What is the …
Q. The work functions of cesium (Cs) and lithium (Li) metals are 1.9 eV and 2.5 eV, respectively. If light of wavelength 550 nm is incident on the surfaces of these two metals, the photoelectric effect will be observed in which of the following cases? Lithium only Neither cesium nor lithium Both cesium and lithium …
Q1: Drift speed of electrons, when 1.5 A of current flows in a copper wire of cross-sectional area 5 mm2 is v. If the electron density of copper is 9 × 1028/m3 the value of v in mm/s is close to (Take charge of electron to be = 1.6 × 10–19 C) (a) 3 (b) 0.2 (c) 2 …
Q1. “The original structure of the Indian Constitution cannot be changed”. In which of the following cases, Supreme Court of India gave this verdict ? (a) The Golak Nath case (b) The Minerva Mills case (c) The Kesavananda Bharati case (d) None of the above (UPSC Prelims 1985) Answer: (c) The Kesavananda Bharati case Explanation: …
Q1. The first Civil Disobedience Movement was started by Gandhiji after the (a) Rowlatt Act of 1919 (b) Jallianwala Bagh massacre in 1919 (c) Chauri Chaura incident in 1922 (d) Arrival of Cripps’ Mission in 1942 (UPSC Prelims 1985) Answer: (a) Rowlatt Act of 1919 Explanation: The Rowlatt Act of 1919, which allowed detention without …
Q1. Write the correct order of occurrence of the following activities while completing the construction of a house Plastering White-washing Electrification Furnishing (a) 1-3-2-4 (b) 3-1-2-4 (c) 3-2-1-4 (d) None of these (UPSC Prelims 1984) Answer: (b) 3-1-2-4 Explanation: The correct sequence is: Electrification (wiring before walls are sealed) Plastering (smoothens surfaces) White-washing (final wall …
Q1. Assertion (A): In 1946 in Bombay the ratings of the Royal Indian Navy rose in open mutiny against the British. Reason (R): The Royal Indian Navy joined the INA (a) A and R both are incorrect (b) A is correct but R is incorrect (c) A and R are correct and R is the …
Q1. Write the correct chronological order of the following events: A. Shifting of capital from Delhi to Daulatabad B. First Battle of Panipat C. Second Battle of Tarain (a) A, B, C (b) C, A, B (c) C, B, A (d) A, C, B Answer: (c) C, B, A Explanation: Chronological order: Second Battle of …
Q1. What is the correct chronological order of the following ? I. First Round Table Conference II. Gandhi-Irwin Pact III. Simon Commission IV. Cripps’ Mission (a) III, I, II, IV (b) I, II, III, IV (c) II, I, III, IV (d) IV, III, II, I (UPSC Prelims 1984) Answer: (a) III, I, II, IV Explanation: …
Q1. What is most significant regarding partition of Bengal in 1905? (a) The English undertook partition without consulting the local population (b) The English established that they were strong people (c) Muslims were separated from other people (d) This paved the way for involvement of people in national movement (UPSC Prelims 1984) Answer: (d) This …