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Questions and Answers
The Lambert-Beer law dictates that the intensity of transmitted light increases exponentially with increases in the thickness of the absorbing sheet.
The Lambert-Beer law dictates that the intensity of transmitted light increases exponentially with increases in the thickness of the absorbing sheet.
False (B)
The half-value layer ($X_{1/2}$) is defined as the thickness of an absorbing material that reduces the original intensity by two-thirds.
The half-value layer ($X_{1/2}$) is defined as the thickness of an absorbing material that reduces the original intensity by two-thirds.
False (B)
The absorption coefficient ($\mu$) is calculated by taking the arithmetic mean of the natural logarithm of the ratio of incident intensity to transmitted intensity versus thickness.
The absorption coefficient ($\mu$) is calculated by taking the arithmetic mean of the natural logarithm of the ratio of incident intensity to transmitted intensity versus thickness.
False (B)
In the simple pendulum experiment, doubling the length of the pendulum will exactly double the period of oscillation.
In the simple pendulum experiment, doubling the length of the pendulum will exactly double the period of oscillation.
When plotting $T^2$ (where $T$ is the period) against the length in the simple pendulum experiment, the slope of the graph is equal to $\frac{4\pi}{g}$, with $g$ being the acceleration due to gravity.
When plotting $T^2$ (where $T$ is the period) against the length in the simple pendulum experiment, the slope of the graph is equal to $\frac{4\pi}{g}$, with $g$ being the acceleration due to gravity.
If air resistance were significant in the simple pendulum experiment, the calculated value of $g$ would be theoretically lower than its actual value.
If air resistance were significant in the simple pendulum experiment, the calculated value of $g$ would be theoretically lower than its actual value.
In the viscous medium experiment a higher coefficient of viscosity results in a slower terminal velocity of the sphere.
In the viscous medium experiment a higher coefficient of viscosity results in a slower terminal velocity of the sphere.
If the density of the sphere is less than the density of the fluid, Stokes' law cannot be applied directly without modifications.
If the density of the sphere is less than the density of the fluid, Stokes' law cannot be applied directly without modifications.
Increasing the diameter of glycerol will increase the coefficient of viscosity of the medium.
Increasing the diameter of glycerol will increase the coefficient of viscosity of the medium.
In the traveling microscope experiment, the measured real depth of the glass slab is affected by both the refractive index of the glass and the ambient temperature.
In the traveling microscope experiment, the measured real depth of the glass slab is affected by both the refractive index of the glass and the ambient temperature.
When measuring the refractive index of a liquid using a traveling microscope, parallax errors during readings affect the measurement of the real depth but not the apparent depth.
When measuring the refractive index of a liquid using a traveling microscope, parallax errors during readings affect the measurement of the real depth but not the apparent depth.
If the liquid used in the traveling microscope experiment has significant chromatic dispersion, the calculated refractive index will be identical regardless of the wavelength of light used.
If the liquid used in the traveling microscope experiment has significant chromatic dispersion, the calculated refractive index will be identical regardless of the wavelength of light used.
In the resonance tube experiment, decreasing the diameter of the resonance tube increases the frequency of the sound.
In the resonance tube experiment, decreasing the diameter of the resonance tube increases the frequency of the sound.
The 'end correction' in a resonance tube experiment accounts for the fact that antinode exists exactly at the open end of the tube.
The 'end correction' in a resonance tube experiment accounts for the fact that antinode exists exactly at the open end of the tube.
Increasing the atmospheric pressure Increases the velocity of sound in the resonance tube experiment if the temperature remains constant.
Increasing the atmospheric pressure Increases the velocity of sound in the resonance tube experiment if the temperature remains constant.
In the convex lens experiment, the magnified image is formed when the lens is positioned closer to the image screen.
In the convex lens experiment, the magnified image is formed when the lens is positioned closer to the image screen.
For a given separation between the object and the screen in the convex lens experiment, there will always be two lens positions that yield clear images.
For a given separation between the object and the screen in the convex lens experiment, there will always be two lens positions that yield clear images.
Based on the lens displacement method you can accurately determine the focal length by analyzing the difference in the two lens positions.
Based on the lens displacement method you can accurately determine the focal length by analyzing the difference in the two lens positions.
The viscous force acting on a sphere is directly proportional to the density of the fluid.
The viscous force acting on a sphere is directly proportional to the density of the fluid.
The absorption coefficient is a dimensionless quantity.
The absorption coefficient is a dimensionless quantity.
Flashcards
Absorption Coefficient
Absorption Coefficient
A measure of how much light is absorbed by a material per unit thickness.
Half-Value Layer (X1/2)
Half-Value Layer (X1/2)
The thickness of a material required to reduce the intensity of radiation passing through it by one-half.
Acceleration of Free Fall (g)
Acceleration of Free Fall (g)
The constant acceleration of a body falling freely due to gravity.
Viscous Force
Viscous Force
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Coefficient of Viscosity
Coefficient of Viscosity
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Refractive Index
Refractive Index
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Focal Length of Convex Lens
Focal Length of Convex Lens
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Resonance
Resonance
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Wavelength (λ)
Wavelength (λ)
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Frequency (f)
Frequency (f)
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Study Notes
Experiment 1: Absorption Coefficient of Glass Using He-Ne Laser
- The experiment aims to measure the absorption coefficient in glass and plastic for a He-Ne laser.
- When monochromatic light passes through an absorber sheet, some of its intensity decreases due to absorption by the sheet.
- The Lambert-Beer law describes this absorption.
- The intensity of transmitted light from the sheet decreases exponentially with increases in thickness.
- The Lambert-Beer law equation is I = Io * exp(-μx) ,
- Io is the incident intensity
- I is the transmitted intensity
- μ is the absorption coefficient
- x is the thickness of the sheet.
- The half-value layer (X1/2) is the thickness of the absorbing material required to reduce the original intensity by one-half.
- From the Lambert-Beer law, X1/2 = 0.693/μ
- To conduct the experiment, set up the device:
- Use a He-Ne laser
- a power meter
- glass and plastic absorber sheets.
- Measure the initial laser intensity (Io) before placing any material, then measure the laser intensity (I) after transmitting through the first glass sheet.
- Place additional sheets and record the intensity each time.
- Plot a graph of intensity versus thickness to evaluate α (absorption coefficient) for glass and plastic plates.
- The slope of the graph will be equal to the absorption coefficient of the He-Ne laser for glass and plastic, respectively.
Experiment 2: Acceleration of Free Fall Using a Simple Pendulum
- This experiment aims to calculate the acceleration of free fall.
- Apparatus:
- pendulum bob
- cotton
- stopwatch
- meter scale
- stand and clamp
- small improvised vice.
- Tie a meter length of cotton to the pendulum bob and suspend it from the vice, ensuring the bob can swing freely with a small angle of about 10 degrees.
- Measure the time for 20 complete oscillations using the stopwatch, repeating the timing and recording multiple times.
- Measure the length (l) of the cotton from the suspension point to the middle of the bob.
- Shorten the pendulum length successively by 5-6 cm, repeating the timing for each new length.
- The periodic time (T) of a simple pendulum is given by T = 2π * sqrt(l/g)
- To calculate g , plot a graph of T²/sec² (ordinates) against l/cm (abscissas).
- Plot a graph of values and draw a best fit line.
- Calculate the slope of the line: slope = (T2² - T1²) / (l2 - l1) which is equal to 4π²/g.
- Calculate the acceleration of free fall: g = 4π²/slope
Experiment 3: Fall of a Body Through a Viscous Medium to Deduce the Coefficient of Viscosity
- This experiment aims to determine the coefficient of viscosity of a viscous medium.
- Apparatus:
- long glass or Perspex tube (1m) closed at one end
- glycerine (fluid)
- micrometer screw gauge
- meter scale
- steel ball bearings
- rubber bands.
- Clamp the tube vertically and fill it with glycerine:
- Place paper collars around the tube
- one near the bottom and another 8-10 cm from the surface.
- Select ten or a dozen balls of the same diameter.
- Adjust the distance between the paper collars to about 60 cm.
- Record this distance then drop a sphere centrally down the tube, measuring the time for it to traverse between the upper edges of the collars using a stopwatch.
- Keep the lower collar fixed, adjust the upper one by 5cm.
- Obtain two values of the time of fall for each new distance.
- Plot a graph of height (h/cm) as ordinates against time (t/sec) as abscissas.
- Calculate the terminal velocity (v) from the graph
- By Stocke's law, viscosity is η = g (ρ – σ)d²/ 18 v
Experiment 4: Refraction Index of Glass and a Liquid by Real and Apparent Depth Using Traveling Microscope
- This experiment aims to determine the refraction index of glass and a liquid by real and apparent depth.
- Apparatus:
- traveling microscope
- glass slabs
- lycopodium powder (wood powder)
- liquid (water)
- vessel.
Refractive Index of Glass
- Place a glass slab on the bench.
- Sprinkle lycopodium powder on its surface: Adjust the microscope to clearly see the powder.
- Place the microscope vertically above, adjust the height, and read the vernier scale (d1).
- Place a second glass slab on top and raise the microscope until the grains are in focus, recording the vernier (d2).
- Sprinkle lycopodium on the second slab, raise the microscope to focus, and record (d3).
Refractive Index of Water
- Sprinkle sand on the flat-bottomed vessel and focus the microscope.
- Record the vernier reading (d1).
- Pour water (1 cm depth) into the vessel and raise the microscope until the sand is in focus, recording the vernier (d2).
- Sprinkle lycopodium on the water surface, raise the microscope to focus, and record (d3).
- Calculate the real depth (d3 - d1) and apparent depth (d3 - d2), then find the refractive index.
Experiment 5: Velocity of Sound by Means of Resonance Tube Closed at One End
- This experiment aims to calculate the velocity of sound using a resonance tube.
- Apparatus:
- resonance tube
- tuning forks
- meter scale.
- Begin the experiment with a short air column in the resonance tube.
- Select the highest frequency fork, strike it, and hold it over the tube.
- Adjust the air column length until resonance occurs (maximum loudness).
- Record the position in the column, and repeat the measurement multiple times.
- Plot the graph of distance by using l/cm again 1/f/sec
- Calculate the average
- The relation is l + ε = c/4f, where ε is the end correction. c is velocity and lambda is measured in meters.
- After transposing, l= c/4 *1/f - ε.
- Therefore the graph of (l/cm) ordinates against -/sec) as abscissas will indicate the value of C.
Experiment 6: Focal Length of a Convex Lens by Displacement Method
- This is to determine the focal length of a converging lens by the displacement method.
- Apparatus:
- convex lens
- holder
- two mounted pains
- meter scale.
- Place the object and image screen at a distance (D) of about 100 cm apart.
- Place the lens between them, adjusting its position to sharply focus the image on the screen.
- Record the position of the lens (d1).
- Move the lens to a second position where a sharp image is formed again, and record the new position (d2).
- Repeat with different separations (D) equal to 90, 80, 70, 60, and 50 cm.
- The focal length is f= (D² - d² )/ 4D.
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