Question

(b) An air wedge of angle \alpha is formed between two glass slides. When illuminated under light of wavelength \lambda from directly above (i.e. at near normal incidence) a series of equally spaced bright line fringes is observed. (i) Derive in terms of horizontal position x from the point of contact the condition for the bright fringes to be observed. (ii) For the fringes in part(i) derive an expression for the separation between fringes \Delta x in terms of wedge angle \alpha. (iii) How will the conditions in parts (i) and (ii) change if a fluid of index n_w, which is greater than the refractive index of glass, fills the gap between the slides? (iv) A pencil tip is pushed into a thin glass slide placed on top of a flat glass block and illuminated with monochromatic light from above. Fringes are formed. Describe and explain with the aid of a diagram what you would expect to see. [13 Marks]

          (b) An air wedge of angle \alpha is formed between two glass slides. When illuminated under light of wavelength \lambda from directly above (i.e. at near normal incidence) a series of equally spaced bright line fringes is observed.
(i) Derive in terms of horizontal position x from the point of contact the condition for the bright fringes to be observed.
(ii) For the fringes in part(i) derive an expression for the separation between fringes \Delta x in terms of wedge angle \alpha.
(iii) How will the conditions in parts (i) and (ii) change if a fluid of index n_w, which is greater than the refractive index of glass, fills the gap between the slides?
(iv) A pencil tip is pushed into a thin glass slide placed on top of a flat glass block and illuminated with monochromatic light from above. Fringes are formed. Describe and explain with the aid of a diagram what you would expect to see.
[13 Marks]

$(b) An air wedge of angle αis formed between two glass slides. When illuminated under light of wavelength λfrom directly above (i.e. at near normal incidence) a series of equally spaced bright line fringes is observed. (i) Derive in terms of horizontal position x from the point of contact the condition for the bright fringes to be observed. (ii) For the fringes in part(i) derive an expression for the separation between fringes Δx in terms of wedge angle α. (iii) How will the conditions in parts (i) and (ii) change if a fluid of index nw, which is greater than the refractive index of glass, fills the gap between the slides? (iv) A pencil tip is pushed into a thin glass slide placed on top of a flat glass block and illuminated with monochromatic light from above. Fringes are formed. Describe and explain with the aid of a diagram what you would expect to see. [13 Marks]$

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