Sound and Light

• Sound is a longitudinal wave created by vibrating objects
• Sound can be classified as either musical tone or noise
• Musical tone is produced by regular vibrations, while noise is produced by irregular vibrations
• Pitch is the highness or lowness of sound
• High frequency sound has a short wavelength, while low frequency sound has a long wavelength
• The speed of sound may change, but its frequency remains the same, so the pitch of sound does not change
• The audible range of frequency for humans is 20 to 20,000 Hz
• Sounds with frequencies lower than 20 Hz are called infrasounds, and sounds with frequencies higher than 20,000 Hz are called ultrasounds
• Loudness is perceived by sound intensity
• The greater the intensity, the louder the sound
• The most common unit used to express loudness is the decibel (dB)
• Quality or timbre is the quality of sound that distinguishes it from other sounds with the same pitch and intensity
• Light was proposed to be a wave by Dutch physicist Christiaan Huygens in 1690
• Light consists of tiny particles emitted by a luminous object according to the corpuscular or particle theory introduced by English physicist Isaac Newton in 1740
• Dual Nature - Light behaves like a particle and a wave according to Louis de Broglie
• Light is an electromagnetic wave, partly magnetic and partly electrical in nature, according to the Electromagnetic Theory by Scottish physicist James Clerk Maxwell
• Light travels through a homogeneous medium in a straight line due to rectilinear propagation
• Visible light is a small portion of the electromagnetic spectrum, lying between the infrared and ultraviolet regions
• The colors of light - visible light consists of different colors that can be perceived by the eye, with each color having its own specific frequency or wavelength
• The speed of light in a vacuum is 299,792,458 m/s or approximately 3x10^8 m/s
• The intensity of light, also known as luminous intensity, describes the rate of speed of light energy per unit area of a surface
• Energy is directly proportional to frequency, as given by the formula E = hf, where E is the energy, h is Planck's constant, and f is the frequency
• Sources of light can be man-made or natural
• Luminous objects are capable of emitting light
• Brightness is the power of light, measuring the amount of light illuminating a surface, and can be expressed with the unit candela (cd)
• Visible Light – has a frequency between 3.93 x 1014 and 7.32 x 1014Hz.
• The intensity of light – also known as the luminous intensity describes the rate of speed of light energy, or power P per unit area A of a surface.