General
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Physics-

A point source causes photoelectric effect from a small metal plate Which of the following curves may represent the saturation photocurrent as a function of the distance between the source and the metal?

Physics-General

  1. c    
  2. d    
  3. a    
  4. b    

    Answer:The correct answer is: d

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    One of the following figures respesents the variation of particle momentum with associated de Broglie wavelength
    a)
    b)
    c)

    One of the following figures respesents the variation of particle momentum with associated de Broglie wavelength
    a)
    b)
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    physics-General
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    Three rods of equal length l are joined to form an equilateral triangle P Q R. O is the mid point of P Q. Distance O R remains same for small change in temperature. Coefficient of linear expansion for P R and R Q is same, i. e. comma blank alpha subscript 2 end subscript but that for P Q is alpha subscript 1 end subscript. Then

    open parentheses O R close parentheses to the power of 2 end exponent equals open parentheses P R close parentheses to the power of 2 end exponent minus open parentheses P O close parentheses to the power of 2 end exponent equals l to the power of 2 end exponent minus open parentheses fraction numerator l over denominator 2 end fraction close parentheses to the power of 2 end exponent
    equals open square brackets l open parentheses 1 plus alpha subscript 2 end subscript t close parentheses close square brackets to the power of 2 end exponent minus open square brackets fraction numerator l over denominator 2 end fraction open parentheses 1 plus alpha subscript 1 end subscript t close parentheses close square brackets to the power of 2 end exponentl to the power of 2 end exponent minus fraction numerator l to the power of 2 end exponent over denominator 4 end fraction equals l to the power of 2 end exponent open parentheses 1 plus alpha subscript 2 end subscript superscript 2 end superscript t to the power of 2 end exponent plus 2 alpha subscript 2 end subscript t close parentheses minus fraction numerator l to the power of 2 end exponent over denominator 4 end fraction left parenthesis 1 plus alpha subscript 1 end subscript superscript 2 end superscript t to the power of 2 end exponent plus 2 alpha subscript 1 end subscript t right parenthesis
    Neglecting alpha subscript 2 end subscript superscript 2 end superscript t to the power of 2 end exponent and alpha subscript 1 end subscript superscript 2 end superscript t to the power of 2 end exponent
    0 equals l to the power of 2 end exponent open parentheses 2 alpha subscript 2 end subscript t close parentheses minus fraction numerator l to the power of 2 end exponent over denominator 4 end fraction open parentheses 2 alpha subscript 1 end subscript t close parentheses rightwards double arrow 2 alpha subscript 2 end subscript equals fraction numerator 2 alpha subscript 1 end subscript over denominator 4 end fraction rightwards double arrow alpha subscript 1 end subscript equals 4 alpha subscript 2 end subscript

    Three rods of equal length l are joined to form an equilateral triangle P Q R. O is the mid point of P Q. Distance O R remains same for small change in temperature. Coefficient of linear expansion for P R and R Q is same, i. e. comma blank alpha subscript 2 end subscript but that for P Q is alpha subscript 1 end subscript. Then

    physics-General
    open parentheses O R close parentheses to the power of 2 end exponent equals open parentheses P R close parentheses to the power of 2 end exponent minus open parentheses P O close parentheses to the power of 2 end exponent equals l to the power of 2 end exponent minus open parentheses fraction numerator l over denominator 2 end fraction close parentheses to the power of 2 end exponent
    equals open square brackets l open parentheses 1 plus alpha subscript 2 end subscript t close parentheses close square brackets to the power of 2 end exponent minus open square brackets fraction numerator l over denominator 2 end fraction open parentheses 1 plus alpha subscript 1 end subscript t close parentheses close square brackets to the power of 2 end exponentl to the power of 2 end exponent minus fraction numerator l to the power of 2 end exponent over denominator 4 end fraction equals l to the power of 2 end exponent open parentheses 1 plus alpha subscript 2 end subscript superscript 2 end superscript t to the power of 2 end exponent plus 2 alpha subscript 2 end subscript t close parentheses minus fraction numerator l to the power of 2 end exponent over denominator 4 end fraction left parenthesis 1 plus alpha subscript 1 end subscript superscript 2 end superscript t to the power of 2 end exponent plus 2 alpha subscript 1 end subscript t right parenthesis
    Neglecting alpha subscript 2 end subscript superscript 2 end superscript t to the power of 2 end exponent and alpha subscript 1 end subscript superscript 2 end superscript t to the power of 2 end exponent
    0 equals l to the power of 2 end exponent open parentheses 2 alpha subscript 2 end subscript t close parentheses minus fraction numerator l to the power of 2 end exponent over denominator 4 end fraction open parentheses 2 alpha subscript 1 end subscript t close parentheses rightwards double arrow 2 alpha subscript 2 end subscript equals fraction numerator 2 alpha subscript 1 end subscript over denominator 4 end fraction rightwards double arrow alpha subscript 1 end subscript equals 4 alpha subscript 2 end subscript
    General
    physics-

    Two circular discs A and B with equal radii are blackened. They are heated to some temperature and are cooled under identical conditions. What inference do you draw from their cooling curves?

    According to Newton’s law of cooling, rate of cooling is given by
    open parentheses fraction numerator negative d T over denominator d t end fraction close parentheses equals fraction numerator e A sigma over denominator m c end fraction left parenthesis T to the power of 4 end exponent minus T subscript 0 end subscript superscript 4 end superscript right parenthesis
    Where c is specific heat of material.
    or open parentheses fraction numerator negative d T over denominator d t end fraction close parentheses proportional to fraction numerator 1 over denominator c end fraction
    i e. comma blankrate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.

    Two circular discs A and B with equal radii are blackened. They are heated to some temperature and are cooled under identical conditions. What inference do you draw from their cooling curves?

    physics-General
    According to Newton’s law of cooling, rate of cooling is given by
    open parentheses fraction numerator negative d T over denominator d t end fraction close parentheses equals fraction numerator e A sigma over denominator m c end fraction left parenthesis T to the power of 4 end exponent minus T subscript 0 end subscript superscript 4 end superscript right parenthesis
    Where c is specific heat of material.
    or open parentheses fraction numerator negative d T over denominator d t end fraction close parentheses proportional to fraction numerator 1 over denominator c end fraction
    i e. comma blankrate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.
    General
    physics-

    Which of the curves in figure represents the relation between Celsius and Fahrenheit temperatures

    fraction numerator C over denominator 5 end fraction equals fraction numerator F minus 32 over denominator 9 end fraction rightwards double arrow C equals open parentheses fraction numerator 5 over denominator 9 end fraction close parentheses F minus fraction numerator 20 over denominator 3 end fraction. Hence graph between ℃ and ℉ will be a straight line with positive slope and negative intercept

    Which of the curves in figure represents the relation between Celsius and Fahrenheit temperatures

    physics-General
    fraction numerator C over denominator 5 end fraction equals fraction numerator F minus 32 over denominator 9 end fraction rightwards double arrow C equals open parentheses fraction numerator 5 over denominator 9 end fraction close parentheses F minus fraction numerator 20 over denominator 3 end fraction. Hence graph between ℃ and ℉ will be a straight line with positive slope and negative intercept
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    maths-

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    The area of circle centred at (1, 2) and passing through (4, 6) is

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    physics-

    The distance between a point source of light and a screen which is 60 cm is increased to 180 cm. The intensity on the screen as compared with the original intensity will be

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    The distance between a point source of light and a screen which is 60 cm is increased to 180 cm. The intensity on the screen as compared with the original intensity will be

    physics-General
    I proportional to fraction numerator 1 over denominator r to the power of 2 end exponent end fraction rightwards double arrow fraction numerator I subscript 2 end subscript over denominator I subscript 1 end subscript end fraction equals fraction numerator r subscript 1 end subscript superscript 2 end superscript over denominator r subscript 2 end subscript superscript 2 end superscript end fraction equals fraction numerator 6 0 to the power of 2 end exponent over denominator 18 0 to the power of 2 end exponent end fraction equals fraction numerator 1 over denominator 9 end fraction
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    Three rods of same dimensions are arranged as shown in figure. They have thermal conductivities K subscript 1 end subscript comma K subscript 2 end subscript and K subscript 3 end subscript. The points P and Q are maintained at different temperatures for the heat to flow at the same rate along P R Q and P Q then which of the following options is correct

    The given arrangement of rods can be redrawn as follows

    It is given that H subscript 1 end subscript equals H subscript 2 end subscript
    rightwards double arrow fraction numerator K A left parenthesis theta subscript 1 end subscript minus theta subscript 2 end subscript right parenthesis over denominator 2 l end fraction equals fraction numerator K subscript 3 end subscript A left parenthesis theta subscript 1 end subscript minus theta subscript 2 end subscript right parenthesis over denominator l end fraction rightwards double arrow K subscript 3 end subscript equals fraction numerator K over denominator 2 end fraction equals fraction numerator K subscript 1 end subscript K subscript 2 end subscript over denominator K subscript 1 end subscript plus K subscript 2 end subscript end fraction

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    The given arrangement of rods can be redrawn as follows

    It is given that H subscript 1 end subscript equals H subscript 2 end subscript
    rightwards double arrow fraction numerator K A left parenthesis theta subscript 1 end subscript minus theta subscript 2 end subscript right parenthesis over denominator 2 l end fraction equals fraction numerator K subscript 3 end subscript A left parenthesis theta subscript 1 end subscript minus theta subscript 2 end subscript right parenthesis over denominator l end fraction rightwards double arrow K subscript 3 end subscript equals fraction numerator K over denominator 2 end fraction equals fraction numerator K subscript 1 end subscript K subscript 2 end subscript over denominator K subscript 1 end subscript plus K subscript 2 end subscript end fraction
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    physics-

    In the following diagram if V subscript 2 end subscript greater than V subscript 1 end subscript then 

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    The maximum kinetic energy (Ek ) of emitted photoelectrons against frequency v of incident radiation is plotted as shown in fig The slope of the graph is equal to

    The maximum kinetic energy (Ek ) of emitted photoelectrons against frequency v of incident radiation is plotted as shown in fig The slope of the graph is equal to

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    In centre of the triangle formed by the lines y = x, y = 3x and y = 8 ­– 3x is

    In centre of the triangle formed by the lines y = x, y = 3x and y = 8 ­– 3x is

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    A lamp rated at 100 cd hangs over the middle of a round table with diameter 3 m at a height of 2 m. It is replaced by a lamp of 25 cd and the distance to the table is changed so that the illumination at the centre of the table remains as before. The illumination at edge of the table becomes X times the original. Then X is

    A lamp rated at 100 cd hangs over the middle of a round table with diameter 3 m at a height of 2 m. It is replaced by a lamp of 25 cd and the distance to the table is changed so that the illumination at the centre of the table remains as before. The illumination at edge of the table becomes X times the original. Then X is

    physics-General
    General
    physics-

    Five lumen/watt is the luminous efficiency of a lamp and its luminous intensity is 35 candela. The power of the lamp is

    Efficiency of light source
    eta equals fraction numerator phi over denominator p end fraction..... (i)
    and L equals fraction numerator phi over denominator 4 pi end fraction..... (ii)
    From equation (i) and (ii)
    rightwards double arrow p equals fraction numerator 4 pi L over denominator eta end fraction equals fraction numerator 4 pi cross times 35 over denominator 5 end fraction almost equal to 88 W.

    Five lumen/watt is the luminous efficiency of a lamp and its luminous intensity is 35 candela. The power of the lamp is

    physics-General
    Efficiency of light source
    eta equals fraction numerator phi over denominator p end fraction..... (i)
    and L equals fraction numerator phi over denominator 4 pi end fraction..... (ii)
    From equation (i) and (ii)
    rightwards double arrow p equals fraction numerator 4 pi L over denominator eta end fraction equals fraction numerator 4 pi cross times 35 over denominator 5 end fraction almost equal to 88 W.
    General
    physics-

    Lux is equal to

    I equals fraction numerator L over denominator r to the power of 2 end exponent end fraction

    Lux is equal to

    physics-General
    I equals fraction numerator L over denominator r to the power of 2 end exponent end fraction
    General
    physics-

    An electric lamp is fixed at the ceiling of a circular tunnel as shown is figure. What is the ratio the intensities of light at base A and a point B on the wall

    I subscript A end subscript equals fraction numerator L over denominator left parenthesis 2 r right parenthesis to the power of 2 end exponent end fraction and I subscript B end subscript equals fraction numerator L over denominator open parentheses r square root of 2 close parentheses to the power of 2 end exponent end fraction cos invisible function application theta
    equals fraction numerator L over denominator 2 r to the power of 2 end exponent end fraction. fraction numerator r over denominator r square root of 2 end fraction equals fraction numerator L over denominator 2 square root of 2   r to the power of 2 end exponent end fraction

    therefore fraction numerator I subscript A end subscript over denominator I subscript B end subscript end fraction equals fraction numerator 2 square root of 2 over denominator 4 end fraction equals fraction numerator 1 over denominator square root of 2 end fraction

    An electric lamp is fixed at the ceiling of a circular tunnel as shown is figure. What is the ratio the intensities of light at base A and a point B on the wall

    physics-General
    I subscript A end subscript equals fraction numerator L over denominator left parenthesis 2 r right parenthesis to the power of 2 end exponent end fraction and I subscript B end subscript equals fraction numerator L over denominator open parentheses r square root of 2 close parentheses to the power of 2 end exponent end fraction cos invisible function application theta
    equals fraction numerator L over denominator 2 r to the power of 2 end exponent end fraction. fraction numerator r over denominator r square root of 2 end fraction equals fraction numerator L over denominator 2 square root of 2   r to the power of 2 end exponent end fraction

    therefore fraction numerator I subscript A end subscript over denominator I subscript B end subscript end fraction equals fraction numerator 2 square root of 2 over denominator 4 end fraction equals fraction numerator 1 over denominator square root of 2 end fraction