Answer:
The position of the first dark spot on the positive side of the central maximum is 1.26 mm.
Explanation:
Given that,
Wavelength of light is 633 nm.
Slit width, d = 0.5 mm
The diffraction pattern forms on a screen 1 m away from the slit. We need to find the position of the first dark spot on the positive side of the central maximum.
For destructive interference :

Y is the distance of the minima from central maximum
Here, n = 1

So, the position of the first dark spot on the positive side of the central maximum is 1.26 mm.
The silver substance is most likely a metal. Your answer is A.
Most of the question 1 is chopped off so I'll try my best to answer.
1ai) In a telephone, the sound is converted into electrical signals before being sent through the wire before converted back into sound.
1aii) Sound travels by the collision between particles. In solids, the particles are closely packed (as compared to air molecules) and thus collide with their neighbors quickly after being disturbed, allowing for sound to be passed on at a faster rate.
b) Can't help much on this one.
Answer: 0 m/s
Explanation: The attached figure shows the position-time graph of a ladybug. We need to find the average speed of the ladybug between t = 4 s to t = 7 s.
We know that, the slope of a position-time graph gives velocity of an object. It can be given by :
In this case, the position of a ladybug at t = 4 s and at t = 7 s is the same i.e. 2 m.
It means its velocity is equal to at this time or we can say that ladybug is at rest.
B is the only answer that makes sense.
A that would mean the car only moves 5 mi/hr
C just doesn't make sense
D the equation never mentions the velocity changing