1. The problem statement, all variables and given/known data A shallowly curved piece of glass is placed on a flat one. When viewed from above, concentric circles appear that are called Newton’s rings. In order to see bright rings, the gap can be: 1. 0 2. 1/4λ 3. 1/2λ 4. λ 2. Relevant equations 1/2 λ occurs when n2>n1 3. The attempt at a solution Why isn't the answer 1/2λ? For ray 1, when air travels into glass there is a 180° phase change. When glass travels back into air, there is no phase change. For Ray 2, it looks like air travels into air (although through glass) back into air so I didn't think there would be a phase change for that.