How is electromagnetic waves useful for cooking food

Explanation:

When the path difference is equal to wave length or its integral multiple, constructive interference occurs . If it is odd multiple of half wave length , then destructive interference occurs.

For constructive interference , path diff = n λ

For destructive interference path diff = ( 2n+ 1 ) λ /2

where λ is wave length of wave , n is an integer.

a )

path diff = 10 cm which is half the wavelength , so maximum destructive interference will occur.

b )

path diff = 15 cm which is neither  half the wavelength nor full wavelength , so in between is the right option.

c )

path diff = 20 cm which is equal to  the wavelength , so maximum constructive  interference will occur.

d)

path diff = 30 cm which is 3 times half the wavelength , so maximum destructive interference will occur.

e)

path diff = 35 cm which is neither integral multiple of half the wavelength , nor integral multiple of wavelength so in between is th eright answer.

f )

path diff = 40 cm which is 2 times the wavelength , so maximum constructive  interference will occur