- Periodic Motion : A motion that repeats itself after regular intervals of time is called periodic motion.
- Example:
- Motion of the Earth around the Sun
- Pendulum motion.
- Example:
- Oscillatory/ Vibratory Motion : A type of periodic motion where a body moves to and fro about a mean position.
- Examples:
- Motion of a pendulum
- Vibration of a tuning fork
- Examples:
- Simple Harmonic Motion (SHM) : If the restoring force is proportional to the displacement and is directed toward the mean position, the motion is called harmonic.
- A special type of oscillatory motion where: 𝐹 = − 𝑘 𝑥
- Where:
- F = restoring force
- 𝑥 = displacement
- 𝑘 = force constant
- Negative sign shows force is opposite to displacement.
- Where:
- A special type of oscillatory motion where: 𝐹 = − 𝑘 𝑥
- Simple Pendulum : A simple pendulum consists of a small bob suspended from a light inextensible string, oscillating back and forth under gravity.
- Time period is independent of mass of the bob.
- SHM is possible only for small angular displacements.
- Maximum velocity occurs at mean position.
- Acceleration is maximum at extreme positions.
- Displacement 𝑥 = 𝐴 sin ( 𝜔 𝑡 + 𝜙 )
- Velocity 𝑣 = 𝐴 𝜔 cos ( 𝜔 𝑡 + 𝜙 )
- Acceleration 𝑎 = − 𝜔2𝑥
- Time Period 𝑇 For pendulum = \[ T = 2\pi \sqrt{\frac{l}{g}} \]
- Sound : Sound is a mechanical longitudinal wave that travels through a medium (solid, liquid, gas) due to vibration of particles.
- Speed of Sound in Different Media Medium
- Air – 343 m/s
- Water – 1500m/s
- Iron- 5000m/s
- Infrasonic
- Frequency Range : <20Hz
- Heard by Humans : No
- Example : Earthquakes, elephant sounds
- Audible
- Frequency Range : 20–20,000Hz
- Heard by Humans : yes
- Example : Human speech, music
- Ultrasonic
- Frequency Range : 20,000Hz
- Heard by Humans : No
- Dogs & bats can hear ultrasonic sounds
- Example : Bat echo, sonar, ultrasound
- Human hearing range: 20 Hz to 20 kHz
- Speed of Sound in Different Media Medium
- Sound Property
- Loudness/ Intensity
- Related to amplitude.
- More amplitude ⇒ Louder sound.
- Measured in decibels (dB).
- Pitch (Shrillness)
- Depends on frequency.
- High frequency ⇒ high pitch (e.g., child’s voice)
- Low frequency ⇒ low pitch (e.g., drum)
- Quality (Timbre)
- Enables us to distinguish two sounds of same pitch & loudness.
- Depends on waveform and overtones.
- Example: Guitar vs piano playing same note.
- Echo and Reflection : Echo occurs when sound reflects from a surface and is heard again.
- Minimum distance for echo: Distance = (𝑣 × 𝑡)/ 2
- Typically, ≥ 17.2 𝑚 in air (for 𝑡 = 0.1 𝑠 t=0.1s).
- Reverberation : Prolonged sound due to multiple reflections.
- Loudness/ Intensity
- SONAR (Sound Navigation and Ranging) : Uses ultrasonic waves for measuring depth in sea.
- Wave : A wave is a disturbance that transfers energy from one point to another without the transfer of matter.
- Wave Equation v=f.λ Where: v = speed of wave, f = frequency , λ = wavelength
- Wave Property
- Wavelength (λ) : Distance between two consecutive crests/troughs
- Crest: Highest point
- Trough: Lowest point
- Unit – meter (m)
- Frequency( 𝑓) : Number of waves passing a point per second
- Unit : hertz (Hz)
- f = 1/ Time
- Amplitude (𝐴) : Maximum displacement from mean position
- Unit : meter (m)
- Time Period (T) : Time taken to complete one cycle
- Unit : second (s)
- Wave speed ( v) : Speed at which wave travels
- Unit : m/s
- Wavelength (λ) : Distance between two consecutive crests/troughs
- Wave Types
- Based on Medium Requirement
- Mechanical : Require a medium to travel
- Sound waves, water waves
- Electromagnetic : Do not require a medium (can travel in vacuum)
- Light, radio, X-rays
- Based on Particle Motion
- Transverse : Particles vibrate perpendicular to wave direction
- Light, water surface
- Longitudinal : Particles vibrate parallel to wave direction Sound waves,
- seismic P-waves
- Transverse : Particles vibrate perpendicular to wave direction
- EM Waves
- All EM waves travel at the speed of light in vacuum:
- They do not require a medium to travel.
- EM waves can travel through vacuum.
- They are transverse waves.
- Both electric (E) and magnetic (B) fields are mutually perpendicular and also perpendicular to the direction of wave propagation.
- They carry energy and momentum
- EM waves can exert pressure (radiation pressure).
- EM waves can show polarization, confirming their transverse nature.
- EM waves behave like normal waves — obeying:
- Laws of Reflection
- Laws of Refraction
- Interference patterns
- Diffraction around obstacles
- EM waves are neutral — they carry no electric charge.
- consist of oscillating electric and magnetic fields
- EM Spectrum : range of all types of electromagnetic radiation arranged according to wavelength or frequency.
- Order of EM Spectrum (by increasing wavelength or decreasing frequency/Energy):
- Gamma rays → X-rays→ Ultraviolet→ Visible light→ Infrared→ Microwaves→ Radio waves
- Visible Light Spectrum : ROYGBIV (Red → Violet)
-
Wavelength range:
-
- Order of EM Spectrum (by increasing wavelength or decreasing frequency/Energy):
| Type | Discoverer | Frequency (Hz) | Uses |
|---|---|---|---|
| Gamma rays | हेनरी बेकुरल | Cancer treatment, nuclear reactions | |
| X-rays | रोन्टजेन | Medical imaging | |
| Ultraviolet | रिटर | Sterilization, vitamin D | |
| Visible light | न्यूटन | Human vision, photosynthesis | |
| Infrared | हर्शेल | Night vision, Remote controls, heat sensors | |
| Microwaves | हेनरी हर्ट्ज़ | Cooking, radar,mobile phones | |
| Radio waves | मार्कोनी | Communication (TV, radio) |