A sonometer wire 100 cm long has a fundamental frequency of 330 Hz. The velocity of propagation of transverse waves on the wire is 1) 330 ms-1 2) 660 ms-1 3) 990 ms-1 4) 115 ms-1 5) 550 ms-1 Answer: 2) 660 ms-1 Solution: For fundamental mode λ/2 =... View Article
In Young’s double-slit experiment, the distance between two sources is 0.1 mm. The distance of the screen from the sources is 20 cm. The wavelength of light used is 5460 Å Then the angular position of the first dark fringe is A. a) 0.08o b) 0.16o c) 0.20o d) 0.32o Answer: b) 0.16o Solution: Δx = dsinθ = λ/2 sinθ... View Article
When light is incident at a polarizing angle, which is completely polarised? a) reflected light b) refracted light c) both d) neither Answer: a) reflected light Solution: When the light is incident at the... View Article
Polaroid glass is used in sunglasses because a) it reduces the light intensity to half on account of polarization b) it is fashionable c) it has good colour d) it is cheaper... View Article
A light beam is incident at θ on an interface of air-glass such that the angle between reflected and the refracted beam is 900. Then θ is a) tan-1 (3/2) b) tan-12 c) tan-1 (3/4) d) tan-1 (4/3) Answer: a) tan-1 (3/2) Solution: When angle between reflected and... View Article
A plane wave of wavelength 6250 Å is incident normally on a slit of width 2 × 10-2 cm. The width of the principal maximum on a screen distant 50 cm will be a) 312.5 × 10-3 cm b) 31.25 × 10-3 cm c) 312 cm d) 312.5 × 10-3 mm Answer: a) 312.5 × 10-3 cm... View Article
The limit of resolution of eye is approximately a) 10 angle b) 1’ angle c) 1 mm d) 1 cm Answer: b) 1’ angle Solution: The resolution of the eye is the smallest... View Article
Diffraction pattern is obtained using red light. What will happen if it is replaced by violet light? a) Bands will disappear b) Bands will become narrow c) Bands will get spaced apart d) Bands will remain unchanged. Answer: b) Bands... View Article
The number of different words which can be formed from the letters of the word LUCKNOW when the vowels always occupy even places is (a) 120 (b) 720 (c) 400 (d) None of these Solution: Total number of letters = 7 Number of vowels = 2 There are 3 even... View Article
Six teachers and six students have to sit around a circular table such that there is a teacher between any two students. The number of ways in which they can sit is (a) 6 ! × 6 ! (b) 5 ! × 6 ! (c) 5 ! × 5 ! (d) None of these Solution: Six students can be arranged around... View Article
The greatest common divisor of 20C1, 20C3, …20C9 is (a) 20 (b) 4 (c) 5 (d) None of these Solution: 20C1 = 20 20C3 = 20 × 19 × 3 = 1140 20C5 = 20C15 = 19... View Article
The expression nCr + 4.nCr-1 + 6.nCr – 2 + 4.nCr – 3 + nCr – 4 is equal to (a) n + 4Cr (b) 2.n + 4Cr – 1 (c) 4.nCr (d) 11.nCr Solution: nCr + nCr-1 = n!/r!(n-r)!] + [n!/(r-1)!(n-r+1)!] =... View Article
Total number of words that can be formed using all letters of the word FAILURE which neither begin with F nor end with E is equal to (a) 3720 (b) 5040 (c) 3600 (d) 3480 Solution: The total number of words formed without any restriction = 7! The... View Article
A shopkeeper sells three varieties of perfumes and he has a large number of bottles of the same size of each variety in this stock. There are 5 places in a row in his showcase. The number of different ways of displaying the three varieties of perfumes in the showcase is (a) 6 (b) 50 (c) 150 (d) None of these Solution: Number of ways of displaying without restriction = 35 Number of ways in... View Article
The number of permutations of the letters of the word HINDUSTAN such that neither the pattern ‘HIN’ nor ‘DUS’ nor ‘TAN’ appears are (a) 166674 (b) 169194 (c) 166680 (d) 181434 Solution: There are 9 letters in HINDUSTAN in which N is repeated twice.... View Article
Find the number of non negative solutions of the system of equations: a + b = 10, a + b + c + d = 21, a + b + c + d + e + f = 33, a + b + c + d + e + f + g + h = 46, and so on till a + b + c + d + … + x + y + z = 208. (a) 22P10 (b) 22P11 (c) 23P13 (d) None of these Solution: Consider the equation a + b = 10 number of solutions of this equation is... View Article
Find the number of non negative integral solutions of equation a + b + c + d = 20. (a) 1800 (b) 1771 (c) 1770 (d) none of the above Solution: Number of non-negative integral solutions of the type of equations x1 + x2 +... View Article
Find the number of non-negative integral solutions of the equation x + y + z = 10. (a) 10C2 (b) 12C2 (c) 11C2 (d) 9C2 Solution: Number of non-negative integral solutions of the type of equations x1 + x2 + … + xn... View Article
There are 18 points in a plane such that no three of them are in the same line except five points which are collinear. The number of triangles formed by these points is : (a) 816 (b) 806 (c) 805 (d) 813 Solution: We need three non collinear points to form a triangle. The number of... View Article
The total number of 3-digit numbers, the sum of whose digits is even, is equal to (a) 450 (b) 350 (c) 250 (d) 325 Solution: Let the three-digit number be n = pqr Sum of digits = p+q+r Since p+q+r... View Article
