Trong phòng thí nghiệm, một sinh viên thực hiện phép đo chiết suất n của một vật liệu X bằng cách đặt lớp vật liệu X dày d 500 nm lên giá đỡ xung quanh là không khí. Chiếu thẳng góc chùm ánh sáng nhìn thấy lên vật liệu X. Quan sát các tia phần xą. sinh viên thấy có 2 tia sáng có bước sóng 4 = 500 nm và 2 = 400 nm còn thiếu trong quang phổ ánh sáng nhìn thấy. a) Tính chiết suất n của vật liệu X b) Đặt lớp vật liệu này lên bản nhôm có chiết suất n 2,75. Lặp lại thí nghiệm tương tự. Hỏi sinh viên quan sát thấy các bước sóng nào trong phổ ánh sáng nhìn thấy? Biết phổ của bước sóng ánh sáng nhìn thấy có bước sóng 380 nm

How much work would a child do while puling a 12-kg wagon a distance of 3m with a 22 n force directed 30 degrees with respect to the horizontal? (a) 82j (b) 52j (c) 109j (d) 95j

Thomas his older brothers, who own a junk yard, on the weekends to earn extra money. he likes to them push broken-down cars to the back of the junk yard because it makes him feel strong. last saturday, they pushed three cars with different weights, and he noticed he used different amounts of force for each one. the cars were the following weights: white car: 2,700 kg red car: 1,500 kg blue car: 2,100 kg think about how much force is needed to move each car. which correctly lists the cars in order from the most to least amount of force needed to move them? a) white, blue, red b) blue, red, white c) red, white, blue d) white, red, blue

Suppose water is leaking from a tank through a circular hole of area ah at its bottom. when water leaks through a hole, friction and contraction of the stream near the hole reduce the volume of water leaving the tank per second to cah 2gh , where c (0 < c < 1) is an empirical constant. a tank in the form of a right-circular cone standing on end, vertex down, is leaking water through a circular hole in its bottom. (assume the removed apex of the cone is of negligible height and volume.) (a) suppose the tank is 20 feet high and has radius 8 feet and the circular hole has radius 2 inches. the differential equation governing the height h in feet of water leaking from a tank after t seconds is dh dt = − 5 6h3/2 . if the height of the water is initially 8 feet, how long will it take the tank to empty? (round your answer to two decimal places.)