Measuring Wavelength of Light with Laser Diffraction Grating

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Questions and Answers

What is the purpose of the rheostat in the Ohm's Law experiment?

To regulate the temperature

To measure the voltage

To vary the resistance (correct)

To measure the current

What is the symbol used to represent electrical resistance in electrical diagrams?

(correct)

What is the name of the German physicist who discovered Ohm's Law?

Newton

Tesla

Ohm (correct)

Einstein

What is the relationship between the current and potential difference in a conductor?

Current is directly proportional to potential difference Signup and view all the answers

What is the name of the law that relates current, potential difference, and resistance in a conductor?

Ohm's Law Signup and view all the answers

What is the unit of measurement for resistance?

Ohms Signup and view all the answers

What is the purpose of the voltmeter in the Ohm's Law experiment?

To measure the voltage Signup and view all the answers

What is the term for substances that offer little resistance to the passage of electric current?

Conductors Signup and view all the answers

What is the main requirement for the liquid used in measuring surface tension?

The liquid used must be transparent Signup and view all the answers

What is the purpose of the experiment using the convex lens by displacement method?

To determine the focal length of a converging lens Signup and view all the answers

What type of lens is used to diverge light waves?

Diverging lens Signup and view all the answers

What is the application of lenses in medical field?

To improve vision in eye glasses Signup and view all the answers

Why does hot water move faster than cold water?

Due to difference in viscosity Signup and view all the answers

What is the CGS unit of dynamic viscosity?

Poise Signup and view all the answers

What is the purpose of using two methods to find the focal length of a convex lens?

To compare the results of the two methods Signup and view all the answers

What is the main error that can occur in measuring the surface tension of a liquid?

The density of the liquid used is non-uniform Signup and view all the answers

What is the primary factor in the pressure-volume relationship of the lung?

Surface tension of the alveoli Signup and view all the answers

What happens to the pressure inside the alveoli when the radius increases during inspiration?

It decreases Signup and view all the answers

What is the role of pulmonary surfactant in the alveoli?

It reduces the surface tension Signup and view all the answers

What happens to the smaller alveoli in the absence of pulmonary surfactant?

They collapse Signup and view all the answers

What is the primary cause of Respiratory Distress Syndrome (RDS) in premature infants?

Absence of pulmonary surfactant Signup and view all the answers

What is the purpose of Experiment (2)?

To determine the viscosity of a medium Signup and view all the answers

What is the effect of temperature on the surface tension of a liquid?

It decreases the surface tension Signup and view all the answers

What is the relationship between the radius and height of a liquid in a capillary tube?

The radius decreases with an increase in height Signup and view all the answers

What is the direction of the frictional force experienced by a body moving in a fluid?

In a direction opposite to the motion Signup and view all the answers

What is the measure of the internal friction of a fluid?

Dynamic viscosity Signup and view all the answers

What is the condition when the sphere falls vertically in the fluid and moves at a constant velocity?

Equilibrium of forces Signup and view all the answers

What is the purpose of step 6 in the experiment?

To gently drop the ball in the liquid Signup and view all the answers

What is the unit of measurement of the coefficient of viscosity of the liquid?

C.G.S. units Signup and view all the answers

What is the purpose of the vertical scale along the height of the jar in the experiment?

To note the least count Signup and view all the answers

What is the condition when the ball falls with an accelerated velocity?

Initially, before it reaches one-third height of the liquid Signup and view all the answers

What is the purpose of steps 7 and 8 in the experiment?

To record the time taken by the ball Signup and view all the answers

What is the preferred laser source used in this experiment?

He-Ne laser Signup and view all the answers

What is the slit spacing of a grating with 100 slits per millimeter?

0.01 mm Signup and view all the answers

What is the purpose of using a diffraction grating in this experiment?

To measure the wavelength of light Signup and view all the answers

What is the angle denoted by θ in Figure 2?

The angle of the second maxima Signup and view all the answers

What is the function of the screen in the experiment?

To measure the diffraction pattern Signup and view all the answers

How many windows per slide are there in the diffraction grating used in this lab?

3 Signup and view all the answers

What is the advantage of using a HeNe laser over other laser sources?

It is more stable and has a higher wattage Signup and view all the answers

What is the purpose of the mounted pin (Object) in the experiment?

To create an object for the light to pass through Signup and view all the answers

What is the advantage of using ultrasound over X-ray in medical imaging?

It gives more information and is less hazardous for the fetus Signup and view all the answers

What is the frequency of a sound wave that has a wavelength of 3 meters, and a speed of 330 meters per second?

1100 Hz Signup and view all the answers

Which of the following is true about sound waves?

They travel fastest in solids Signup and view all the answers

What is the unit of measurement for sound intensity?

W/m² Signup and view all the answers

What is the purpose of an audiogram?

To test hearing thresholds and pain thresholds Signup and view all the answers

What is the mathematical representation of the frequency of a wave?

f=1/T Signup and view all the answers

What is the term for the distance between successive compressions or rarefactions in a sound wave?

Wavelength Signup and view all the answers

What is the term for the energy carried by a sound wave per unit area and per unit time?

Intensity Signup and view all the answers

Which of the following is NOT a characteristic of sound waves?

They can travel through a vacuum Signup and view all the answers

What is the term for the ratio of the intensity of a sound wave to a reference intensity?

Intensity ratio Signup and view all the answers

What is the frequency range of sound waves that can be heard by the human ear?

20 Hz to 20 KHz Signup and view all the answers

What is the effect of intense infrasonic noise on the human body?

It can cause respiratory impairment, aural pain, fear, visual hallucinations, and chills Signup and view all the answers

What is the application of infrasound in medicine?

It is used to study heart mechanical function Signup and view all the answers

What is the characteristic of infrasound that allows it to travel long distances?

Low absorption and large wavelength Signup and view all the answers

What is the frequency range of ultrasound used in medical imaging?

Above 20 KHz Signup and view all the answers

What is the definition of sound in medicine?

All of the above Signup and view all the answers

What is the property of sound waves that allows them to transfer energy without transferring matter?

Mechanical nature Signup and view all the answers

What is the medium required for sound waves to propagate?

Elastic material Signup and view all the answers

What is the characteristic of sound waves that allows them to be classified into infrasound, audible sound, and ultrasound?

Frequency Signup and view all the answers

What is the application of sound waves in medicine, specifically in diagnostics?

It is used to diagnose various diseases using ultrasound and stethoscope Signup and view all the answers

What is the primary function of the bell in a stethoscope?

To serve as an impedance matcher between body and air Signup and view all the answers

What is the relationship between the intensity of a sound and its loudness?

Loudness increases with increasing intensity Signup and view all the answers

What happens to a sound wave when it is applied perpendicularly to an interface between two media with different acoustic impedance?

The wave is partially reflected and partially transmitted Signup and view all the answers

What is the purpose of selecting a specific bell size and diaphragm tension in a stethoscope?

To selectivity pick up certain frequency ranges Signup and view all the answers

What is the term for the degree of sensation of sound produced in the ear?

Loudness Signup and view all the answers

What happens to the reflected wave when the acoustic impedance of the two media is significantly different?

The reflected wave undergoes a phase change Signup and view all the answers

What is the relationship between the natural frequency of the bell and the tension of the diaphragm?

The natural frequency increases with increasing tension Signup and view all the answers

What is the purpose of sound reflection and transmission in medical applications?

To image internal organs Signup and view all the answers

What is the characteristic of sound that is perceived as high or low?

Pitch Signup and view all the answers

What is the condition required for complete transmission of a sound wave to a second medium?

The acoustic impedance of the two media must be identical Signup and view all the answers

Study Notes

Experiment 6: Measuring the Wavelength of Light using Laser Diffraction Grating

Purpose: To measure the wavelength of a HeNe laser using a diffraction grating
Apparatus:
- Scale (100 cm)
- Laser source (HeNe)
- Holders
- Screen
- Mounted pin (Object)
- Diffraction Grating (100-600 lines per millimeter)
Theory:
- A diffraction grating consists of a large number of equally spaced parallel slits
- The space between any two lines is transparent to light and acts as a separate slit
- The grating has three windows per slide (100, 300, and 600 lines per millimeter)
- The geometry of light after passing through the diffraction grating is shown in Figure 1
- The angle θ denotes the second maxima, and there is a θn for each xn

Experiment 5: Ohm's Law

Aim: To investigate Ohm's Law
Apparatus:
- Power supply "E"
- Ammeter
- Rheostat
- Constant resistance "R"
- Voltmeter
Theory:
- Electrical resistance opposes the passage of electric current
- The symbol R denotes the electrical resistance of the tungsten filament in the light bulb
- Ohm's Law states that the current in a conductor is directly proportional to the potential difference and inversely proportional to the resistance of the conductor
- The relationship between V and I is represented in Figure 3

Experiment 3: Lenses

Objective: To find the focal length of a convex lens using two methods
A. Focal Length Converging Lens (Displacement Method)
Theory:
- A lens is a piece of glass or other transparent material shaped to produce an image by refracting light
- Lenses are used in many purposes (eye glasses, cameras, telescopes, microscopes, and even in our eyes)
- Convex lenses are converging lenses, while concave lenses are diverging lenses

Experiment 2: Viscosity of Liquid

Purpose: To determine the viscosity of a medium using a small sphere falls with a constant terminal velocity
Apparatus:
- Long glass tube (50 cm long)
- Glycerin
- Meter Scale
- Small Sphere
- Rubber bands
- Magnet
- Stop Watch
Theoretical background:
- A body moving in a fluid feels a frictional force in a direction opposite to its direction of motion
- The dynamic viscosity η measures the internal friction of the fluid
- Stokes derived an expression for the frictional force on a sphere moving in a fluid

Experiment 1: Surface Tension

Objective: To measure the surface tension of a liquid
Medical Application:
- The alveoli in the lungs are similar to interconnected bubbles
- The surface tension of the liquid lining the alveoli is an important factor in the pressure-volume relationship of the lung
- Pulmonary surfactant lowers the surface tension by getting between water molecules, reducing their ability to attract each other by hydrogen bonding
- The absence of surfactant in the lungs of some newborn infants, especially premature, is the cause of Respiratory Distress Syndrome (RDS)

General Properties of Sound

A sound wave is a pattern of disturbance caused by energy traveling away from the source of sound.
Sound is a mechanical disturbance that propagates through an elastic material medium with a definite velocity.
In air, sound can be defined as a local increase (compression) or decrease (rarefaction) of pressure relative to atmospheric pressure.

Sonic Spectrum

Sonic spectrum can be classified into three frequency ranges: infrasound, audible sound, and ultrasound.
The human ear can hear sounds in the range of roughly 20 Hz to 20 KHz.
Infrasound refers to sound frequencies below 20 Hz, produced by natural phenomena like earthquake waves and atmospheric pressure changes.
Infrasound can travel long distances without losing much power, and its effects can be difficult to minimize.
Infrasound can produce clear symptoms including respiratory impairment, aural pain, fear, visual hallucinations, and chills.
Infrasound can also be used to study heart mechanical function, revealed by the seismocardiogram.
Ultrasound is the frequency range above 20 KHz, used clinically in various specialties.

Effect of Sound on Human Hearing

The human ear can distinguish two characteristics of sound: loudness (or volume) and pitch.
Loudness is the degree of sensation of sound produced in the ear, dependent on its intensity.
Pitch refers to whether a sound is high (sharp) or low.

Sound Reflection and Transmission

When a sound wave is applied perpendicularly to the interface between two media with different acoustic impedance, a portion of the wave will pass through and another will reflect.
The ratio of reflected (or transmitted) and incident waves can be measured.
If the acoustic impedance of the two media is equal, there is no reflected wave, and transmission to the second medium is complete.
If the acoustic impedance of the two media is different, the sign change indicates a phase change of the reflected wave.

Applications of Sound in Medicine

Stethoscopes are diagnostic instruments that amplify sounds made by the body from the heart, lungs, or other body sites.
The bell of a stethoscope serves as an impedance matcher between the body and the air in the tube.
The frequency of the sounds must resonate in the bell membrane, and the natural frequency of the bell depends on its size and diaphragm tension.
Stethoscopes can be used to selectivity pick up certain frequency ranges (e.g., low-frequency heart murmurs, high-frequency lung sounds).

Properties of Sound Waves

The speed of sound is given by the formula: c = √(T/ρ)
The frequency of a sound wave is denoted by the formula: f = 1/T
The wavelength of a sound wave is denoted by the formula: λ = c/f
The intensity of a sound wave is the energy carried by the wave per unit area and per unit time, expressed by the maximum change in pressure.

Sound Intensity Level [Ratio]

The intensity of a sound wave can be compared to a reference intensity using the formula: Intensity ratio = I / I0
The absolute value of sound intensity cannot be measured directly.

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Description

This laboratory experiment measures the wavelength of a HeNe laser using a diffraction grating. Students will learn how to use a diffraction grating and calculate the wavelength of light. The experiment is designed to demonstrate the principles of light and optics.