Interjections in Hindi can be used to express surprise :

Oh you came! ओह  क्या तुम आ गए

Other interjections in this same category are :

अरे 

ओहो

धत

धत तेरे की 

Joy can be expressed by :

Oh what a beautiful place! वाह वाह क्या सुंदर जगह है

Another example of this kind of interjection is :

आहा 

Sorrow and grief is expressed by :

Alas what happened! हाय यह क्या हुआ

Other interjections of this kind :

हा 

उफ

अफसोस

Here are some other interjections :

Stop! बस कीजिए 

Be careful! सावधान 

Get away! हट