Suppose that the central diffraction envelope of a double-slit diffraction pattern contains 15 bright fringes and the first diffraction minima eliminate (are coincident with) bright fringes. how many bright fringes lie between the first and second minima of the diffraction envelope?

6 bright fringes.

Step-by-step explanation:

We know bright interference fringes occur at

d sinθ =mλ where m is an integer.

Here d = 13×a/2(since there are 13 bright fringes ).

Then for first minimum which occurs at angle θ_1 then a sinθ_1 = λ (m=1)

for second minimum which occurs at angle θ_2 then a sinθ_2 = 2λ (m=2)

then we calculate the values of m for which  θ_1 < θ<  θ_2 for  sinθ_1 < sin_θ<  sinθ_2

λ < 2×mλ/13 <2λ

that is 1<2m/13 <2

the satisfied values of m are 7,8,9,10,11,.12. Thus there are 6 bright fringes.

rick has $1400 and sally has $1500

step-by-step explanation:

to find amount of money rick has after 10 years :

principal = $1000 , time = 10 years , rate = 4% annually

to find amount of money sally has after 10 years :

her friend gives to pay her $50 per year, therefore money she has after 10 years = 50 × 10 = $500

also, sally gets $1000 after 10 years,

therefore, total amount of money sally has after 10 years = 500 + 1000 = $1500

so, after 10 years : rick has $1400 and sally has $1500

if you are looking for the unit rate then the answer would be 9 because unit rate is distance divided by time.

step-by-step explanation: