A pinhole camera<span> is a simple </span>camera<span> without a lens but with a tiny aperture, a</span>pinhole<span> – effectively a light-proof box with a small hole in one side. Light from a scene passes through the aperture and projects an inverted image on the opposite side of the box, which is known as the </span>camera<span> obscura effect.</span>
Answer:

☯ Question :
- How fast is a wave travelling if it has a wavelength of 7 meters and a frequency of 11 Hz?
☯ 
☥ Given :
- Wavelength ( λ ) = 7 meters
- Frequency ( f ) = 11 Hz
☥ To find :
☄ We know ,

where ,
- v = speed of sound
- f = frequency
- λ = wavelength
Now, substitute the values and solve for v.
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✑ Additional Info :
- Frequency : The number of complete vibrations made by a particle of a body in one second is called it's frequency. It is denoted by the letter f . The SI unit of frequency is hertz ( Hz ).
- Wavelength : The distance between two consecutive compressions or rarefactions of a sound wave is called wavelength of that wave. It is denoted by λ ( lambda ) and it's SI unit is m.
- Speed of a sound wave : The distance covered by a sound wave in one second is called speed of sound wave. It depends on the product of wavelength and frequency of the wave.
Hope I helped!
Have a wonderful time! ツ
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Partial eclipse, Annular eclipse,
Total Eclipse and Hybrid Eclipse are the four different
types of the eclipses. When the Sun and Moon are exactly in line with the Earth, the annular eclipse occurs.
The new moon is invisible from the earth and it is silhouetted against the sun,
this can only be seen in annular eclipse. Annular word means ring shaped, we
can see a dark ring of fire in annular eclipse. It has five different stages
that are first contact, second contact, maximum eclipse, third contact and 4th
contact.