What is an AM / FM wave?
The modulation method that changes the carrier amplitude according to the modulation signal is called amplitude modulation. The radio wave after amplitude modulation is called amplitude modulation wave. It maintains the frequency characteristics of the high-frequency carrier, but the shape of the envelope is similar to the signal waveform. The amplitude of the AM wave is determined by the strength of the modulated signal. The amplitude modulation wave is represented by the English letter AM.
The modulation method that changes the carrier frequency according to the modulation signal is called frequency modulation. The magnitude of the modulated wave frequency change is determined by the size of the modulated signal, and the period of the change is determined by the frequency of the modulated signal. The amplitude of the modulated wave remains unchanged. The waveform of the FM wave is like a spring compressed unevenly. The FM wave is represented by the English letter FM.
At present, the frequency band used by medium-wave broadcasting is roughly 550kHz-1600kHz, which is mainly propagated by ground waves, and is also accompanied by some sky waves; FM radio broadcasting uses ultra-short wave (very high frequency) radio waves to transmit signals, and the frequency of use is about 88MHz-108MHz. The signals are mainly transmitted by space waves.
Accessories for cameras are mainly for care, protection, special effects and functions.
Lens hood: used on the end of a lens to block the sun or other light source to prevent glare and lens flare (see also matte box).
Lens cap: covers and protects the lens during storage.
Lens adapter: sometimes called a step-ring, adapts the lens to other size filters.
Lens filters: allow artificial colors or change light density.
Lens extension tubes allow close focus in macro photography.
Flash equipment: including light diffuser, mount and stand, reflector, soft box, trigger and cord.
Care and protection: including camera case and cover, maintenance tools, and screen protector.
Large format cameras use special equipment which includes magnifier loupe, view finder, angle finder, focusing rail /truck.
Battery and sometimes a charger.
Some professional SLR could be provided with interchangeable finders for eye-level or waist-level focusing, focusing screens, eye-cup, data backs, motor-drives for film transportation or external battery packs.
Tripod, microscope adapter, cable release, electric wire release.
Dew shield - Prevents moisture build up on the lens.
Camera Accessories,Selfie Stick Adaptor,Smartphone Selfie Stick,Threw Hold Camera Accessories
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