Question

can a completely transparent object cast a shadow
answer yes

Answer 1

Yes it will, shadow is made when an object blocks light. In a simpler way, the object must be opaque or translucent to make a shadow. A transparent object will not create any shadow, as light will pass straight through the object,  but such transparent objects do not allow all the light to pass through them, they still interact with light through refraction. Refraction is what makes transparent cups visible to our eyes. Refraction also enables clear objects to cast shadows. The key principle regarding refraction is that light is bent when the index of refraction differs from one object to other. Air and glass are different materials and have different indices of refraction. Light therefore bends when it goes from air into glass, such as at the surface of a glass lens. Refraction does not happen inside a glass lens because the material inside the lens is uniform. Refraction happens at the surface of a glass lens because that is the only place where the index of refraction differs. Take off your eyeglasses and place them on the table at night under the illumination of a single lamp and you will see a distinct shadow caused by the transparentlenses.In a scientific term Photons(light) interact with an object by some combination of reflection, absorption and transmission.
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Answer 2

Answer:

No, a transparent object can't cast shadow since the light rays pass pass through it completely.